Omit include parameter from OpenAPI schema when left unused

[arttuperala]

Description of the Change

Omits the #/components/parameters/include reference from operation parameters if the given serializer does not implement included_serializers.

At least the documentation makes it seem that included_serializers is the only official way of adding include to the parameters, so I assume checking it like this would be safe.

Checklist

• PR only contains one change (considered splitting up PR)
• unit-test added
• documentation updated
• CHANGELOG.md updated (only for user relevant changes)
• author name in AUTHORS

[sliverc]

Thanks for this addition. I am happy to merge this.

Just for your information the OpenAPI schema support within DJA will be deprecated in the near future, see discussion at #1082. The recommended way will be to use drf-spectecular-json-api. Best have a look there and see whether you can support the project.