service: Authorization

# Propose

Implement a service that would be responsible for handling authorization.
It would be nice if this service could hold some claims for a user authorization, so it knows what this user can access, like features or services.

This service would have some routes like:

- [ ] `/authorization/authorize`
- [ ] `/authorization/authenticate`
- [ ] `/authorization/user`
- [ ] `/authorization/user/claims`

No files, tests, or entry points are named. Start by reviewing the repository's existing service layout and Docker Compose configuration, then clarify the authorization model, claims, authentication behavior, and route contracts for /authorization/authorize, /authorization/authenticate, /authorization/user, and /authorization/user/claims. Done means the agreed service behavior and acceptance tests are implemented.

Written by the indexing model from the issue text.