closes https://github.com/TryGhost/Team/issues/3259
- API output mappers (soon to be serializers) are meant to work based on allowlist set of output properties. Having the allowlist early on will allow to track the API evolution consistently.
refs https://github.com/TryGhost/Team/issues/3167
- This is scaffolding for collections API. Contains wiring for service wrapper, e2e test, and a browse endpoint
- Adds basic implementation of the GET /collections endpoint to build up upon
- Note, there are no permissions in this version as they will be added in later stages of development with migrations etc
