Fixes #8854: Remote auth default groups added to new remote auth users

[huntabyte]

Fixes: #8854

Added a custom pipeline handler function per python-social-auth docs

This pipeline handler assigns the default group(s) to remote auth users. Successfully tested with Microsoft Azure AD, however, there is nothing particular related to Azure AD in this configuration.

[jeremystretch]

Awesome work, thanks for tackling this!

[HolySephi]

This change removes the possibility to define my own SOCIAL_AUTH_PIPELINE in configuration.py and thus removes the function to assign roles from auth claims as groups via custom_pipeline. Removing thhis static SOCIAL_AUTH_PIPELINE from settings.py allows my own pipeline to run again.
Bug: SOCIAL_AUTH_PIPELINE from configuration.py does not overwrite this SOCIAL_AUTH_PIPELINE from settings.py

if you are interested - this is the custom_pipeline to set auth claim roles to groups (tested and used with AzureAD):

from django.contrib.auth.models import Group

class AuthFailed(Exception):
    pass`

def set_role(response, user, backend, *args, **kwargs):
    try:
        role = response['roles'][0]
    except KeyError:
        raise AuthFailed("No role assigned")

    try:
        group = Group.objects.get(name="{}".format(role))
    except Group.DoesNotExist:
        raise AuthFailed("Unknown role")

and adding 'netbox.custom_pipeline.set_role' to my own SOCIAL_AUTH_PIPELINE