* Add tests

* Fix some link previews being incorrectly generated from different prior links

PR #12403 added a cache to avoid redundant queries when the OEmbed endpoint can
be guessed from the URL. This caching mechanism is not perfectly correct as
there is no guarantee that all pages from a given domain share the same
OEmbed provider endpoint.

This PR prevents the FetchOEmbedService from caching OEmbed endpoint that
cannot be generalized by replacing a fully-qualified URL from the endpoint's
parameters, greatly reducing the number of incorrect cached generalizations.

* Remove Salmon and PubSubHubbub endpoints

* Add error when trying to follow OStatus accounts

* Fix new accounts not being created in ResolveAccountService

* Fix undefined method error in sidekiq

Body can be not nil but still be empty, which causes a
`NoMethodError: undefined method `[]' for nil:NilClass` further in the
code. This checks for an empty body to avoid the issue.

* Fix codeclimate issue

* Add failing test for windows-1251 link cards

* Ignore low-confidence CharlockHolmes guesses

Fixes #9466

* Fix no method error when charlock holmes cannot detect charset

* No need to re-require sidekiq plugins, they are required via Gemfile

* Add derailed_benchmarks tool, no need to require TTY gems in Gemfile

* Replace ruby-oembed with FetchOEmbedService

Reduce startup by 45382 allocated objects

* Remove preloaded JSON-LD in favour of caching HTTP responses

Reduce boot RAM by about 6 MiB

* Fix tests

* Fix test suite by stubbing out JSON-LD contexts

* Add equals_or_includes_any? helper in JsonLdHelper

* Support arrays in JSON-LD type fields for actors/tags/objects.

* Spec for resolving accounts with extension types

* Style tweaks for codeclimate

* Added #link_header spec

* Added #call spec

* Delete spec of private methods

* Added #call spec

* Fix an error when actor json couldn't be fetched in ResolveRemoteAccountService

* Add specs

* Specs for language detection

* Use CharlockHolmes instead of NKF

* Correct mistakes

* Correct style

* Set hint_enc instead of falling back and strip_tags

* Improve specs

* Add dependencies

* Do not default the format in ProviderDiscovery

The format should be determined when discovering, as it is in the current
implementation, and it is a flaw if it is not determined.

* Spec ProviderDiscovery

* Fix #2119 - Whenever about to send a HTTP request, normalize the URI

* Add test for IDN request in FetchLinkCardService

* Perform IDN normalization on domains before they are stored in the DB