Maven Virtual Registry: Maven API endpoint

🔭 Issues plan

1. Maven Virtual Registry: Database models (#467972 - closed).
2. Maven Virtual Registry: Permissions policy (#467977 - closed).
3. Maven Virtual Registry: Registry models API (#467979 - closed).
4. Maven Virtual Registry: Maven API endpoint (#467982 - closed). 👈 You're here.
5. Maven Virtual Registry: Cache logic (#467983 - closed).
6. Maven Registry: Cached responses destruction (#468113 - closed).
7. Improve workhorse dependencyproxy logic (#461561 - closed).
8. Maven Virtual Registry: Documentation (#468115 - closed).
9. Maven Virtual Registry: Performance review (#468116 - closed).
10. Maven Virtual Registry: feature flag cleanup (#468117).

🗒 Description

Route	Notes
GET /api/v4/virtual_registry/packages/maven/:registry_id/*path/:file_name	Users will need to configure /api/v4/virtual_registry/packages/maven/:registry_id as the registry endpoint.

To give a concrete example here, on gitlab.com, with a maven registry with id 555, I'll configure Maven clients with.

https://gitlab.com/api/v4/virtual_registry/packages/maven/555

No caching logic in this implementation. Simply workhorse sendurl to the upstream and that's it.

🔮 Other considerations

• No caching logic, it will be implemented in the next issue.
• Authentication: PAT, CI job token, DeployToken
• Authorization: permission read_virtual_registry. See Maven Virtual Registry: Permissions policy (#467977 - closed).
• Use a feature flag