Expose provider information in the tags

[AetherUnbound]

Description

Related to #431

In order to differentiate the source of various tags, both creator- and machine-generated, we plan to expose the provider information to the tags block in the API results.

This can be done by adding a new field, unstable__provider, to the TagSerializer here (note that we'll need to set source="provider", since the field in the database is provider):

openverse/api/api/serializers/media_serializers.py

Line 442 in 3ed38fc

class TagSerializer(serializers.Serializer):

We are using unstable__provider here so that we have the flexibility to remove or change the parameter name down the line without affecting API versioning. The parameter itself can be stabilized after this project is complete.

Additional context

See: https://docs.openverse.org/projects/proposals/rekognition_data/20240423-implementation_plan_machine_generated_tags_api.html#expose-provider-in-tags