The feature is controlled by a switch on the provider.
Emails are sent if the email changes during the sync.
We skip syncing the username/email if there would be a conflict.

- Remove usage of django.urls.patterns
- Change urls tuples to lists
- Make all string view names callables

Since we have started integrating with more clients, we have found that the usernames
that get passed are not compatible with our username restrictions. This PR introduces
a function to clean usernames to make them compatible, particularly in the auto registration
case.

ENT-600

Refactoring: Use format with named variables

PSA was monolothic, now split, with new features, like
a DB-backed partial pipeline. FB OAuth2 version also upped.

Partial pipelines don't get cleared except when necessary.
They persist for special cases like change of browser while
still mid-pipeline (i.e. email validation step).

Refactor, cleanup, and update of a lot of small things as well.

PLEASE NOTE the new `social_auth_partial` table.

When authenticating using an SAML IdP, gather additional user
data besides what is standard. Requires admin to input JSON
in settings to recognize the additional user data.

Closes ENT-361.

This change fixes a bug where OAuth2 Provider Configs only show
up on logistration if the provider's `provider_slug` matches a
valid OAuth2 backend name.

Closes ENT-320.