Add an endpoint to return schema dependencies

**Motivation**
With #5026 done, we need another endpoint for schemas to get them an insight on their dependencies

**Acceptance criteria**
1. The user must have read access on the schemas of the project
2. The endpoint returns information on the imported schemas and ontologies: their project, their id, their revision at the time of the schema creation/update and if they are a direct depedency or not.

Review the implementation delivered for #5026 to find the existing schema endpoint patterns and entry points. Trace how schema imports and ontologies are represented, then define the endpoint behavior against the acceptance criteria: enforce read access and return project, id, creation/update revision, and direct-dependency information.

Written by the indexing model from the issue text.