Convert drf-yasg to drf-spectacular.

[SkylordA]

The platform currently uses drf-yasg which is used for swagger/OpenAPI 2.0 schema generation. We want to support generic OIDC providers such as authentik (mentioned in #1223).

However authentik does not support "implicit" flow type entirely, does not support the response_type="token", and does not fully allow grant_type="password", as these are now deprecated/no longer best practice. The recommended method to use for authentication is PKCE, which is an extension of flow type "authorizationCode", which is an OpenAPI 3.0 flow type.

Therefore we need to upgrade from drf-yasg to drf-spectacular before adding support for authentik and other OIDC providers, and upgrading keycloaks authentication.

Info on these 3rd party DRF packages for OpenAPI support: https://www.django-rest-framework.org/topics/documenting-your-api/
Info on implicit flow: https://oauth.net/2/grant-types/implicit/
Info on password grant: https://oauth.net/2/grant-types/password/