feat: support passing login query string to oauth authorize redirect

[scarbeau]

Description

This commit modifies the AuthOAuthView login function, introducing the option to preserve inbound request parameters and include them on the authorize redirect url created by the OAuth provider. This functionally is controlled by a new configuration bool AUTH_OAUTH_PRESERVE_LOGIN_QUERY. This value defaults to false to ensure this change is opt-in only and should have no impact on current usage.

This feature is needed to better support login via a federated IdPs (e.g., Cognito with multiple federated providers). For example, consider the following flask endpoints:

/login/cognito?identity_provider=customer1-okta
/login/cognito?identity_provider=customer2-auth0
/login/cognito?identity_provider=customer3-onelogin

With this commit, the resulting redirects will be (some parameters excluded for readability):

https://DOMAIN.amazoncognito.com/oauth2/authorize?client_id=X&redirect_uri=https://app/oauth-authorized/cognito&identity_provider=customer1-okta
https://DOMAIN.amazoncognito.com/oauth2/authorize?client_id=X&redirect_uri=https://app/oauth-authorized/cognito&identity_provider=customer2-auth0
https://DOMAIN.amazoncognito.com/oauth2/authorize?client_id=X&redirect_uri=https://app/oauth-authorized/cognito&identity_provider=customer3-onelogin

Note the identity_provider parameter on each authorize url. This will allow Cognito (or other OAuth2 providers) to immediately redirect the client to the applicable IdP, improving overall user experience.

ADDITIONAL INFORMATION

• Has associated issue:
• Is CRUD MVC related.
• Is Auth, RBAC security related.
• Changes the security db schema.
• Introduces new feature
• Removes existing feature

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 79.61%. Comparing base (c65e067) to head (ebd0aa0).

Files	Patch %	Lines
flask_appbuilder/security/views.py	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2222      +/-   ##
==========================================
+ Coverage   73.81%   79.61%   +5.79%     
==========================================
  Files          72       72              
  Lines        8754     9032     +278     
==========================================
+ Hits         6462     7191     +729     
+ Misses       2292     1841     -451     

Flag	Coverage Δ
python	79.61% <0.00%> (+5.79%)	⬆️

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