Cherry-picked d2528b26b6da34f34b5d7a392e263428d3c09d69
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.
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.
