Ensure the api-server is backwards compatible

[bisgaard-itis]

Is there an existing issue for this?

• I have searched the existing issues

Planned changes

• After upgrading to pydantic v2 we need to ensure that the api-server is backwards compatible in order to not break already deployed services which depend on the api-server (see 🎨 Add examples to pydantic response models #6658 (comment))
• We also need to setup a githook which generates the openapi.json of the api-server before committing so that we detect changes before they are rolled out.