Distinguish LIST-only paths in OpenAPI

[digivava]

Fixes #12283

Differentiates between paths that only support LIST (including GET w/ list=true query params), and those that support both LIST and plain GET.

According to my testing, at this point in time there are 77 List-only endpoints and 10 that support both.

[kalafut]

LGTM, but I'll let one of the devs approve. You might want to generate our full openapi spec using this branch and pop it into a validator (e.g. I used to use https://editor.swagger.io/) just to make sure we're spec-compliant.

[digivava]

You might want to generate our full openapi spec using this branch and pop it into a validator (e.g. I used to use https://editor.swagger.io/) just to make sure we're spec-compliant.

Good catch there. It looked fine to me since it was valid json but now that I paste it in there, I see that it's giving me this for every List-only path:

Structural error at paths./ad/library.get.parameters.0
should NOT have additional properties
additionalProperty: enum

The output json looks like this:

      parameters:
        - name: list
          description: Must be set to `true`
          in: query
          schema:
            type: string
          required: true
          enum:
            - 'true'

Should I perhaps remove the newly added enum field and just keep the required: true, since that's still programmatically useful enough to differentiate from a list+read endpoint and makes the validator happy?

[kalafut]

Are you validating as OpenAPI 3 (I don't recall how that is set in the swagger tool)? Because I think the enum you added looks ok, per https://swagger.io/docs/specification/data-models/enums/ ?

[kalafut]

Scratch that. I think the enum needs to move under schema.