Parameter that is required, but optional on the ModelField is has the "null" type included

[gabn88]

Describe the bug
A model with a public_access_uuid (UUIDField(blank=True,null=True)) is used as a path paramater, let's say:

/api/order/{public_access_uuid}

This results in a scheme:

      parameters:
        - in: path
          name: public_access_uuid
          schema:
            type:
              - string
              - 'null'
            format: uuid
          required: true

As you can see the 'null' and required: true do bite eachother. And because of this scheme, the swagger-ui cannot be used for this endpoint and gives Required field is not provided.

To Reproduce
Add a ModelField like about.
Add a ModelSerializer with that field as lookup_field.

Expected behavior
The null type can be omitted.

I tried to explicitly add a public_access_uuid = serializers.UUIDField, with different options (required=True, allow_null=False), but that did not help.

I have now overridden it with:

    parameters=[
        OpenApiParameter(
            "public_access_uuid", OpenApiTypes.UUID, OpenApiParameter.PATH
        ),  # path variable was overridden
    ],

And that works, but it would be nice to have it work out of the box.

[gabn88]

This seems to have to do with using OpenAPI 3.1.0. If I load our schema in the OpenAPI editor it also shows an error on those lines, while the OpenAPI next-editor does not stumble over these lines.