Query parameter mapped via MapParams is not present in OpenAPI spec

[nya1]

Using Goa version v3.7.2

Design example to reproduce

The expected metadata Attribute of MapOf(String, String) type is
mapped to the HTTP transport as MapParams("metadata")

The metadata query parameter can be passed to the URL as the following:
GET /multiply/?metadata[testKey]=val

The service will correctly receive map[testKey:val], but the OpenAPI generated
it's not listing the metadata in the endpoint.

Expected

metadata query parameter to be present in OpenAPI like the other mapped attributes, example:

      parameters:
      - in: query
        name: metadata
        description: this should be on openapi
        required: false
        schema:
          type: object
          additionalProperties: true
          example:
            testKey: val
        style: deepObject

You can find all files / setup to reproduce the issue: https://github.com/nya1/goa-mapparams-repro

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[raphael]

Thanks for the nice repro, this is fixed in #3381