Implement basic Claim Service API

To kick off the work on the Topology Service / Claim Service, we can start by implementing a basic Claim Service API on the Topology Service. The Claims should not be validated or persisted. This work should unblock the work on the Client side GitLab App.

See the API in the relevant EPIC, and the POC work in the references.

References

• GitLab POC (Client) Implementation: !146528 (closed)
• Topology Service POC (Server) https://gitlab.com/gitlab-org/tenant-scale-group/pocs/topology-service/-/blob/main/proto/claim_service.proto?ref_type=heads