auth: Use generic Django authentication backends from swh-auth
Django authentication backends based on the use of Keycloak and OpenID
Connect have been moved to the swh-auth
module and turned into generic
backends in order to easily reuse them in any Django application.
So remove all code and tests that have been moved in swh-auth
and
configure swh-web
to use the generic authentication backends.
That diff will fail to build until a new swh-auth
version is tagged.
Related to #3150 (closed)
Depends on swh-auth!19 (closed)
Migrated from D5367 (view on Phabricator)