* Fix #2195 - Set locale to error pages

* Fix #2195 - Cut duplicate process into one method

Create MediaAttachment but without actual file download when domain is blocked with reject_media set to true
Clean up old media files when creating a new domain block with reject_media set to true
Return remote_url in media attachments API if local file is not present
Undo domain block action in admin UI
Ability to enable reject_media from admin UI

An attempt to open a brand new Mastodon instance configured
as SINGLE_USER_MODE=true will cause an exception.

Enable temporary registration if we have no users in the database

Fixes #1817

Setting of locale in controller extracted to Localized concern,
the doorkeeper authorized applications controller moved under
custom namespace with inclusion of Localized, which resolves the
"it sometimes appears in a different random language" bug

used from nginx when Rails fails.

from accounts/tags because it's a terribly inefficient way to paginate
large sets of data

by updating it at least every 24h if the user visits the site

before loading new one, cache notifications API, fix missing follow button
on public profiles

production as it's very verbose and not very useful

in the pool, adding a throttle of 60rpm per IP, adding mini profiler, adding
admin status to users