* 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

* Replace OEmbed Rabl template with serializer

* Replace initial state rabl with serializer

* Fix #4058 - Use a long-lived cookie to keep track of user-level sessions

* Fix tests, smooth migrate from previous session-based identifier

* add a system_font_ui setting on the server

* Plug the system_font_ui on the front-end

* add EN/FR locales for the new setting

* put Roboto after all other fonts

* remove trailing whitespace so CodeClimate is happy

* fix user_spec.rb

* correctly write user_spect this time

* slightly better way of adding the classes

* add comments to the system-font stack for clarification

* use .system-font for the class instead

* don't use multiple lines for comments

* remove trailing whitespace

* use the classnames module for consistency

* use `mastodon-font-sans-serif` instead of Roboto directly

In from_redis method, statuses retrieved from the database was mapped to
the IDs retrieved from Redis. It was equivalent to order from high to low
because those IDs are sorted in the same order.
Statuses are ordered with the ID by default, so we do not have to reorder.
Sorting statuses in the database is even faster since the IDs are indexed
with B-tree.

* Faster emojify() algorithm, avoid regex replace

* add semicolon

* Fix #3910 - Require OTP authentication to disable 2FA. Also, remove ability
to generate new OTP backup codes *after* initial backup codes were handed
out during activation

* Restore recovery code re-generation

* Improve display of some 2FA elements

Also domain_block fabricator now sets unique domains

* Add overview of active sessions

* Better display of browser/platform name

* Improve how browser information is stored and displayed for sessions overview

* Fix test

* feat: Revocable sessions

* fix: Tests using sign_in

* feat: Configuration entry for the maximum number of session activations

* Introduce domains method to Account relation

Account had followers_domains method, which was excessively specific.
Let relation of Account have domains method instead.

* Move follow_mapping in Account to AccountInteractions

* Introduce shared examples for AccountAvatar inclusion

* Cover Account more

* Fix regression from #3842

Simplify the query by omitting all direct statuses. Private statuses
are allowed because they are from accounts we are following (so
by definition)

Resolves #3887 (alternative)

* Adjust test

The classes using Status.as_home_timeline, namely Feed and
PrecomputeFeedService are expected to filter direct statuses as
FanOutWriteService does, but their filtering were incomplete or missing.

This commit solves the problem by filtering direct statuses in
as_home_timeline as the other similar methods such as as_public_timeline
does.

This fixes a random spec failures since commit
d55f2072.

This fixes below bugs:

* pipe characters being counted as RTL character
* only first word being checked

Rename Activitypub to ActivityPub

* Whitelist allowed classes for federated statuses

Allowed classes are currently:

 - Any microformats class (h/p/u/dt/e-*)
 - the classes mention, hashtag, ellipses and invisible.

this last one is somewhat suspect, but Mastodon currently uses it to render hidden link text.

resolved #3790

* Fix code style

Fix regression from #3490 - filter out hidden statuses from ancestors/descendants even if the viewer is anonymous (#3752)

account before removing content for quicker feedback to end-users