Relates to #6125, #6099

* Add GET /api/v1/instance/peers API to reveal known domains

* Add GET /api/v1/instance/activity API

* Make new APIs disableable, exclude private statuses from activity stats

* Fix code style issue

* Fix week timestamps

* Make host_meta/webfinger replies cacheable (fixes #6100)

Drop common code for handling users and sessions as webfinger queries
are very basic, public APIs.

Also explicitly mark results as cacheable with “expires_in”.

* Add “Vary: Accept” header for caching since content-negociation is used

Getting Started column obtained many links, and it became much taller.
Because of its height, Getting Started column required long scrolling on
devices with small screen, such as 4 inch phones and 10 inch laptops.

This change moves the mastodon which took large space on the column to
drawer column. The drawer column has only the compose form and has more
space.

* removed references to hideOnMobile in column_link and getting_started

* add mute, block, conversationMute actions to detailed status dropdown (fixes #1226)

* remove unused withDismiss in detailed status

* Add aria-autocomplete='list' in Textaria

ref: https://www.w3.org/TR/wai-aria-1.1/#aria-autocomplete

* Make detect empty string brefore assign upload description

* Change code elements in keyboard-shortcuts component to kbd

* Add validation for onMuteNotifications

* Reduce motion for boost animation

Fixes #5833

* Fix ternary expression

* Remove onSave method in mapped properties for column_settings

* Make web_push_subscription.register an action

* removed references to hideOnMobile in column_link and getting_started

* move keyboard shortcuts back below blocked users

Deleted users are technically suspended, but the code displaying their status
in the admin interface was broken and displayed a javascript object holding
translations of the possible user roles instead.

* Add aria-autocomplete='list' in Textaria

ref: https://www.w3.org/TR/wai-aria-1.1/#aria-autocomplete

* Make detect empty string brefore assign upload description

* Change code elements in keyboard-shortcuts component to kbd

* Update Korean translation

* Translate Korean for javascript

* Add missing translations on simple_form

* Add Slovak translation

* Slovak translation: i18n-normalize

* i18n: (zh-CN) Change `工作人员` (staff) to `管理人员`
Suggested by @Gargron at https://github.com/tootsuite/mastodon/pull/6005#discussion_r156678109

* i18n: (zh-CN) Change `协管` to `监察员`

* i18n: (zh-CN) Fix all "Are you" questions

* i18n: (zh-CN) Various improvements

* i18n: (zh-CN) Final clean-up

* i18n: (zh-CN) Change translation for 500

* i18n: (zh-CN) Remove spaces between time distances

* i18n: (zh-CN) Improve translations

* Last minute Dutch strinfupdate

* Last minute Dutch strings update

* Fixing Weblate output errors

* Fixing Weblate output errors

* Fixing more Weblate rubish

Weblate is also changing some " to ' - I think that is not a problem

* Fixing more weblate stuff

* Fixing

* Update nl.yml

* Fix overflowing emojis on some devices

* Quit visible and add padding

* Adjust empty list timeline message (#5997)

* Adjust empty list timeline message (#5997)

* Add filters to admin UI for custom emojis (#6003) + #6004

* Update fr.yml

* Excahnge the order of spoiler-input and unlocked warning

* Fix trailing whitespace

* Redesign tootbox

* Move counter into compose-form__buttons-wrapper

Change font and remove shadow
Refactor sass codes of compose-form

* Translated using Weblate (Dutch)

Currently translated at 100.0% (522 of 522 strings)

Translation: Mastodon/Backend
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/backend/nl/

* Translated using Weblate (French)

Currently translated at 99.8% (521 of 522 strings)

Translation: Mastodon/Backend
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/backend/fr/

* Translated using Weblate (Catalan)

Currently translated at 100.0% (257 of 257 strings)

Translation: Mastodon/React
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/frontend/ca/

* Translated using Weblate (Catalan)

Currently translated at 99.4% (519 of 522 strings)

Translation: Mastodon/Backend
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/backend/ca/

* Translated using Weblate (Japanese)

Currently translated at 99.4% (519 of 522 strings)

Translation: Mastodon/Backend
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/backend/ja/

* Translated using Weblate (Portuguese)

Currently translated at 100.0% (257 of 257 strings)

Translation: Mastodon/React
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/frontend/pt/

* Translated using Weblate (Dutch)

Currently translated at 100.0% (257 of 257 strings)

Translation: Mastodon/React
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/frontend/nl/

* Translated using Weblate (Galician)

Currently translated at 100.0% (257 of 257 strings)

Translation: Mastodon/React
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/frontend/gl/

* Translated using Weblate (Japanese)

Currently translated at 99.6% (520 of 522 strings)

Translation: Mastodon/Backend
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/backend/ja/

* Translated using Weblate (Japanese)

Currently translated at 100.0% (56 of 56 strings)

Translation: Mastodon/Preferences
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/simple_form/ja/

* Translated using Weblate (Arabic)

Currently translated at 40.0% (209 of 522 strings)

Translation: Mastodon/Backend
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/backend/ar/

* Translated using Weblate (Arabic)

Currently translated at 100.0% (257 of 257 strings)

Translation: Mastodon/React
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/frontend/ar/

* Translated using Weblate (Polish)

Currently translated at 99.8% (521 of 522 strings)

Translation: Mastodon/Backend
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/backend/pl/

* Added translation using Weblate (Galician)

* Translated using Weblate (Portuguese (Brazil))

Currently translated at 99.0% (517 of 522 strings)

Translation: Mastodon/Backend
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/backend/pt_BR/

* Translated using Weblate (Portuguese (Brazil))

Currently translated at 100.0% (257 of 257 strings)

Translation: Mastodon/React
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/frontend/pt_BR/

* Translated using Weblate (Galician)

Currently translated at 100.0% (56 of 56 strings)

Translation: Mastodon/Preferences
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/simple_form/gl/

* Added translation using Weblate (Galician)

* Translated using Weblate (Galician)

Currently translated at 100.0% (56 of 56 strings)

Translation: Mastodon/Preferences
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/simple_form/gl/

* Translated using Weblate (Galician)

Currently translated at 22.6% (17 of 75 strings)

Translation: Mastodon/Doorkeeper
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/doorkeeper/gl/

* Translated using Weblate (Portuguese)

Currently translated at 100.0% (257 of 257 strings)

Translation: Mastodon/React
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/frontend/pt/

* Translated using Weblate (Portuguese)

Currently translated at 66.0% (37 of 56 strings)

Translation: Mastodon/Preferences
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/simple_form/pt/

* Translated using Weblate (Japanese)

Currently translated at 99.6% (520 of 522 strings)

Translation: Mastodon/Backend
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/backend/ja/

* Translated using Weblate (Japanese)

Currently translated at 100.0% (257 of 257 strings)

Translation: Mastodon/React
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/frontend/ja/

* Translated using Weblate (Japanese)

Currently translated at 100.0% (43 of 43 strings)

Translation: Mastodon/Devise
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/devise/ja/

* Translated using Weblate (Portuguese (Brazil))

Currently translated at 99.6% (520 of 522 strings)

Translation: Mastodon/Backend
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/backend/pt_BR/

* Translated using Weblate (Portuguese (Brazil))

Currently translated at 100.0% (257 of 257 strings)

Translation: Mastodon/React
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/frontend/pt_BR/

* Translated using Weblate (Arabic)

Currently translated at 100.0% (257 of 257 strings)

Translation: Mastodon/React
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/frontend/ar/

* Translated using Weblate (Arabic)

Currently translated at 48.8% (21 of 43 strings)

Translation: Mastodon/Devise
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/devise/ar/

* Translated using Weblate (Arabic)

Currently translated at 98.2% (55 of 56 strings)

Translation: Mastodon/Preferences
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/simple_form/ar/

* Translated using Weblate (Portuguese)

Currently translated at 73.2% (41 of 56 strings)

Translation: Mastodon/Preferences
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/simple_form/pt/

* Translated using Weblate (Portuguese)

Currently translated at 100.0% (43 of 43 strings)

Translation: Mastodon/Devise
Translate-URL: https://weblate.joinmastodon.org/projects/mastodon/devise/pt/

* i18n-tasks normalize && yarn manage:translations

* Restore wrongfully deleted files

* i18n: (zh-CN) Remove spaces in time distances

* i18n: (zh-CN) Update translations for #5997

* i18n: (zh-CN) Add translation for #6004
also change translation of `staff` from `管理员` to `工作人员`

* i18n: (zh-CN) Add translations for #6003

* i18n: (zh-CN) Normalization

* Add staff filter to admin UI for accounts, remove obsolete columns

* Only display OStatus section in admin UI for accounts when OStatus data

* Fix #5952 - NameError (regression from #5762)

* Fix

* Add aria-autocomplete='list' in Textaria

ref: https://www.w3.org/TR/wai-aria-1.1/#aria-autocomplete

* Make detect empty string brefore assign upload description

The preview image would be useful to embed in timeline.

Avoid error when the service returns a mostly valid oembed, but has no
url in it, causing a MethodError: undefined method `url'
for #<OEmbed::Response::Photo:0x000056505def9620>

* Change conditional to avoid nil into string error in sidekiq
When obtaining information about users with mastodon in a different
subdomain, sidekiq was giving out a 'no implicit conversion of nil into String'

* Use presence instead of blank? with ternary.
Following suggestion on PR