Make subclassing reusable

[stsewd]

I'm extracting the code from Integrations to make it reusable for #5323. I'll move this to another file, but I'd like to see if we want to follow this path first.

Also, tests are passing for subclassing

https://github.com/rtfd/readthedocs.org/blob/3218c808e87206983c4eb3ce4faceddbcc0f7aa3/readthedocs/rtd_tests/tests/test_integrations.py#L169-L169

[ericholscher]

This is a good refactor. I wonder if we should be using an existing solution for this instead?

https://django-polymorphic.readthedocs.io/en/stable/
https://django-model-utils.readthedocs.io/en/latest/managers.html#inheritancemanager

both look like good options.

[stsewd]

Ok, not sure how to block the review here, but this is still a work in progress p:

Need to move this code to another place.

[stsewd]

Love it https://django-polymorphic.readthedocs.io/en/stable/, it's what we need. Maybe we can use it only for the new models (#5323) and create a separete issue/pr to adapt current models? Here is the migration guide https://django-polymorphic.readthedocs.io/en/stable/migrating.html

If so, we can close this PR and I can update the other PR to use that package

[humitos]

Maybe we can use it only for the new models (#5323) and create a separete issue/pr to adapt current models? Here is the migration guide django-polymorphic.readthedocs.io/en/stable/migrating.html

This makes sense to me.

[stsewd]

I opened #5394 to track this