Ensure OpenAPI specification is generated correctly

Description

Currently the OpenAPI specification generated by the spectacular management command is not correct, and does not include the API endpoints. This should be fixed so that the API specification can be generated correctly.

Further details

Task list

Acceptance criteria

• OpenAPI specification generates correctly from poe manage spectacular
• Add unit test to verify OpenAPI generation produces valid output and includes expected endpoints

Links/references

• https://pypi.org/project/openapi-spec-validator/