Retrieve subjects by schema id

[weeco]

Who is this for and what problem do they have today?

The endpoint GET /schemas/ids/{id}/subjects is currently not supported. This requires a brute-force (retrieve all schemas) to figure out what subject a given schema id belongs to.

What are the success criteria?

GET /schemas/ids/{id}/subjects is supported and fully compliant with the reference implementation.

Why is solving this problem impactful?

In Redpanda Console we could show the subject names of subjects that reference a schema. The referencedby endpoint already exists, but only returns schema ids which are not very meaningful to human users.

Additional notes