OpenAPI (Swagger) schema shouldn't provide choices for Status references

[glennmatthews]

Environment

• Nautobot version (Docker tag too if applicable): all

Steps to Reproduce

Currently the OpenAPI schema generated by Nautobot will list a specific enum of permissible options for references to Status objects, e.g.

    Circuit:
      ...
      properties:
        ...
        status:
          type: object
          properties:
            value:
              type: string
              enum:
              - active
              - decommissioned
              - deprovisioning
              - offline
              - planned
              - provisioning
            label:
              type: string
              enum:
              - Active
              - Decommissioned
              - Deprovisioning
              - Offline
              - Planned
              - Provisioning

The problem, of course, is that this is NOT actually a hard-coded list of choices, it's determined at schema generation time from whatever set of Status objects happen to be defined. The moment a user adds, deletes, or edits any Status record, this part of the schema becomes inaccurate.

Most likely, the best solution here (albeit probably a breaking, i.e. 2.0 change) will be to change the status API field serializers so that they use a nested serializer like any other foreign-key reference, i.e. instead of:

      "status": {
        "value": "active",
        "label": "Active"
      }

they instead use:

    {
      "id": "64864569-9d3f-4b17-bb00-47296d9ccd0e",
      "display": "Active",
      "url": "https://demo.nautobot.com/api/extras/statuses/64864569-9d3f-4b17-bb00-47296d9ccd0e/",
      "name": "Active",
      "slug": "active",
    },

[glennmatthews]

This would also fix any schema generation warnings that can be seen after customizing the Statuses in your installation, e.g.:

(drf_spectacular.W001) Warning: enum naming encountered a non-optimally resolvable collision for fields named "status". The same name has been used for multiple choice sets in multiple components. The collision was resolved with "Status5a0Enum". add an entry to ENUM_NAME_OVERRIDES to fix the naming.

[glennmatthews]

Straightforward enough to implement, thanks to extensive use of mixin classes. The bigger challenge will be making it backwards-compatible with older API versions - there are a lot of models with Statuses, so that'll be a lot of versioned serializers.

[glennmatthews]

Implemented for 2.0 in #3225.