For some reason (probably some problem with one of the serializers) we
sometimes lack an id attribute for a promise that we get for a repo
relationship on build. Because of that doing `build.get('repo.id')` may
sometimes return undefined. A temporary workaround is to make sure that
we always can access the `repository_id` property.
This commit adds adapters and serializers for v3, but also a fallback
serializer for v2, which allows to handle v2 and v3 payloads at the same
time. This is needed, because when we use v3 endpoint for one of the
models (in this case repo), we can also get embedded records of other
types (like branch or build).
This commit refactors repo-actions support to use components and make
the implementation much simpler. It also fixes a bug with buttons being
displayed when they shouldn't be.
