Cherry-picked d2528b26b6
Conflicts:
- `app/serializers/initial_state_serializer.rb`:
Upstream changed stuff, we had extra attributes.
Applied upstream changes while keeping our extra attributes.
- `app/serializers/rest/instance_serializer.rb`:
Upstream actually moved that to `app/serializers/rest/v1/instance_serializer.rb`,
so updated that file by keeping our extra attributes, and took upstream's
version of `app/serializers/rest/instance_serializer.rb`.
- `spec/views/about/show.html.haml_spec.rb`:
Took upstream's version.
* Change references to tootsuite/mastodon to mastodon/mastodon
* Remove obsolete test fixture
* Replace occurrences of tootsuite/mastodon with mastodon/mastodon in CHANGELOG
And a few other places
The cache store is explicitly used by some specs, but they were not
isolated and therefore not reliable. This fixes the issue by clearing
the cache after each specs.