Add django-ninja as REST API option

[browniebroke]

Description

• Change use_drf=y/n option to rest_api=None/DRF/Django Ninja
• Update all existing mentions of DRFs to the new style
• Add a few jobs on CI to cover REST API + username field combinations
• Add a similar level of functionality and testing as DRF with Django Ninja

Checklist:

• I've made sure that tests are updated accordingly (especially if adding or updating a template option)
• I've updated the documentation or confirm that my change doesn't require any updates

Rationale

While DRF is a solid option, Django Ninja has gained popularity over the years and is the only other option listed in the ecosystem page.

Fix #4923

Disclaimer

I'm not super familiar with Django Ninja, so I might not have gone with the most idiomatic way to write view and schema. That might be an area of focus if you're more familiar with the framework.

[soccer99]

I pulled this for my newest project and its working well for me!