Feature: Custom SSO Adapter and Config Loading for Flexible SSO

[chrismaddalena]

This includes the changes from PR #501 and uses those changes to support loading SSO configurations without requiring any editing of the config files from the repository.

This also includes a customized social login adapter for django-allauth. The adapter includes a pre_social_login() check that look at the user's primary email address to perform the following:

• If en existing account has the same email address, the social login is allowed and the accounts are connected
• If multiple accounts share the same email address, the user is redirected with an error message
• If no account is found, the social login results in a new account being created (if registration is enabled)

We could potentially check all email addresses attached to user accounts or require email addresses be verified. That may come in a later update.

If SOCIAL_ACCOUNT_ALLOW_REGISTRATION is enabled (set to True) Ghostwriter will create a new account for the incoming user. A custom populate_user() sets the user's first, last, and full name fields and sets the username from the the SSO provider or the first half of the email address.

The custom is_open_for_signup() also checks a new SOCIAL_ACCOUNT_DOMAIN_ALLOWLIST config option. If this option is filled-in, Ghostwriter will only allow a new account to be created if the incoming user's email address matches a domain in this allowlist.

[codecov]

Codecov Report

Attention: Patch coverage is 65.21739% with 8 lines in your changes missing coverage. Please review.

Project coverage is 91.93%. Comparing base (ff61393) to head (19ec9c2).
Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
ghostwriter/users/forms.py	42.85%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #502      +/-   ##
==========================================
- Coverage   91.96%   91.93%   -0.04%     
==========================================
  Files         314      315       +1     
  Lines       18158    18183      +25     
==========================================
+ Hits        16699    16716      +17     
- Misses       1459     1467       +8     

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[chrismaddalena]

Closed in favor of #513 that includes these changes.