* Fix issues with POSIX::Spawn, Terrapin and Ruby 3.0

Also improve the Terrapin monkey-patch for the stderr/stdout issue.

* Fix keyword argument handling throughout the codebase

* Monkey-patch Paperclip to fix keyword arguments handling in validators

* Change validation_extensions to please CodeClimate

* Bump microformats from 4.2.1 to 4.3.1

* Allow Ruby 3.0

* Add Ruby 3.0 test target to CircleCI

* Add test for admin dashboard warnings

* Fix admin dashboard warnings on Ruby 3.0

* Fix media processing getting stuck on too much stdin/stderr

See thoughtbot/terrapin#5

* Remove dependency on paperclip-av-transcoder gem

* Remove dependency on streamio-ffmpeg gem

* Disable stdin on ffmpeg process

* Fix how to change connection pool for rails 6

* Fix to match the code elsewhere

occured -> occurred

* Update devise-two-factor to unreleased fork for Rails 6 support

Update tests to match new `rotp` version.

* Update nsa gem to unreleased fork for Rails 6 support

* Update rails to 6.1.3 and rails-i18n to 6.0

* Update to unreleased fork of pluck_each for Ruby 6 support

* Run "rails app:update"

* Add missing ActiveStorage config file

* Use config.ssl_options instead of removed ApplicationController#force_ssl

Disabled force_ssl-related tests as they do not seem to be easily testable
anymore.

* Fix nonce directives by removing Rails 5 specific monkey-patching

* Fix fixture_file_upload deprecation warning

* Fix yield-based test failing with Rails 6

* Use Rails 6's index_with when possible

* Use ActiveRecord::Cache::Store#delete_multi from Rails 6

This will yield better performances when deleting an account

* Disable Rails 6.1's automatic preload link headers

Since Rails 6.1, ActionView adds preload links for javascript files
in the Links header per default.

In our case, that will bloat headers too much and potentially cause
issues with reverse proxies. Furhermore, we don't need those links,
as we already output them as HTML link tags.

* Switch to Rails 6.0 default config

* Switch to Rails 6.1 default config

* Do not include autoload paths in the load path

It appears assets are built during image build, and they shouldn't need
to be rebuilt, since we now have reproducible builds.

* Improve account counters handling

* Use ActiveRecord::Base::sanitize_sql to pass values instead of interpolating them

Keep using string interpolation for `key` as it is safe and using
“ActiveRecord::Base::sanitize_sql_hash_for_assignment” would require stitching
bits of SQL in a way that is not more easily checked for safety.

* Add migration hook to catch PostgreSQL versions earlier than 9.5

Mastodon::MigrationHelpers has been forked from Gitlab a long time ago, but
Mastodon has never supported using a MySQL database.

Removing MySQL support from Mastodon::MigrationHelpers makes it a little easier
to maintain. In particular, it removes code that would need updating with
Rails 6.

Hopefully fixes #15922

Also update support up to latest database schema version

* Use ActiveRecord::Result#to_ary instead of deprecated to_hash

They do the same thing, and to_hash has been removed from Rails 6.1

* Explicitly name polymorphic indexes to workaround a bug in Rails 6.1

cf. https://github.com/rails/rails/issues/41693

* Fix incorrect usage of “foreign_key” in migration script

* Use `ActiveModel::Errors#delete` instead of deprecated clear method

* Fix link headers tests on Rails 6.1

Rails 6.1 adds values to the Link header by default, thus it is not a
LinkHeader object anymore. Fix the test to parse the Link header instead
of assuming it is a LinkHeader.

* Prepare Mastodon for zeitwerk autoloader (Rails 6)

Add inflections and rename/move a few classes.

In particular, app/lib/exceptions.rb and app/lib/sanitize_config.rb
were manually loaded while still in autoload paths.

* Add inflection for Url → URL

* Fix misuse of foreign_type

* Fix use of removed "add_template_helper"

* Use response.media_type instead of response.content_type in tests

* Fix CSV export controller test on Rails 6

Rails 6 sets a "filename*" field in the Content-Disposition header to
explicitly encode the filename as UTF-8.

This changes checks the first part of the Content-Disposition header so
it matches in both Rails 5 and Rails 6.

* Fix emoji formatting with Rails 6

* Make emoji output more idiomatic and robust

* Switch from redis-rails gem to built-in Rails redis cache storage

The "ends_with?" method is just a Rails alias of Ruby's "end_with?" method.
Using the latter makes the code less brittle.

"headers" is provided by Rails, Rack can't rely on it

* Drop dependency on secure_headers, use always_write_cookie instead

* Fix cookies in Tor Hidden Services by moving configuration to application.rb

* Instead of setting always_write_cookie at boot, monkey-patch ActionDispatch

* Added .deepsource.toml

* Removed bad use of `alias`

* Fixed operand order in the binary expression

* Prefixed unused method arguments with an underscore

* Replaced the old OpenSSL algorithmic constants with the newer strings initializers.

* Removed unnecessary UTF-8 encoding comment

Fixes #15635

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

* Use Regex#match?

* Replace =~ too

* Avoid to call match? from Nil

* Keep value of Regexp.last_match

* Use Rails' index_by where it makes sense

* Fix tests

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

* Optimize map { ... }.compact

using Enumerable#filter_map, supported since Ruby 2.7

* Add poyfill for Enumerable#filter_map

* Fix maintenance script not re-indexing some indexes on textual values

Fixes #15475

* Refresh instance view at the end of the maintenance script run

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

* disable NewCops

* update TargetRubyVersion

* Fix Lint/MissingSuper for ActiveModelSerializers::Model

* Fix Lint/MissingSuper for feed

* Fix Lint/FloatComparison

* Do not use instance variables

* Improve Emoji import

Skip macOS '._' shadow files in tar archive to speed up import

* Fix codeclimate format issue with whitespace

* Update lib/mastodon/emoji_cli.rb

suggestions from Gargron to improve comment

Co-authored-by: Eugen Rochko <eugen@zeonfederated.com>

* Update emoji_cli.rb

Remove extraneous comment (macOS-specific comment now with correct line)

Co-authored-by: Eugen Rochko <eugen@zeonfederated.com>

* Fix being able to import more than allowed number of follows

Without this commit, if someone tries importing a second list of accounts to
follow before the first one has been processed, this will queue imports for
the two whole lists, even if they exceed the account's allowed number of
outgoing follows.

This commit changes it so the individual queued imports aren't exempt from
the follow limit check (they remain exempt from the rate-limiting check
though).

* Catch validation errors to not re-queue failed follows

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

* Fix external user creation failing when invite request text is required

Also fixes tootctl-based user creation.

* Add test about invites when invite request text is otherwise required

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

- `pluck_each` cannot be used this way with `group`
- typo

Co-authored-by: Claire <claire.github-309c@sitedethib.com>