server/app/interfaces/repository.py: Implement missing `/description` endpoint

[moritzsommer]

Current Situation

Currently, server endpoint /description", methods=["GET"], endpoint=self.not_implemented is not implemented.

According to the AAS Repository Service OpenAPI Specification, the endpoint should return the self-describing information of the API implementation.

[...]
summary: Returns the self-describing information of a network resource (ServiceDescription)
[...]
responses:
  '200':
    description: Requested Description
    content:
      application/json:
        schema:
          $ref: 'https://api.swaggerhub.com/domains/Plattform_i40/Part2-API-Schemas/V3.0.1#/components/schemas/ServiceDescription'
[...]

This issue specifies #439.

Proposed Change

We should evaluate and, if feasible, implement GET /description according to the specification.