Add support for using Social Login (OAuth) for reauthentication (veri…

[jwag956]

…fy).

Also - change documentation to refer to Social Login (OAuth) which is more user-facing friendly Change the button labels to 'Continue with github' - will do the login button in another PR. Improved JSON payload for reauthentication responses, /us-verify, and /verify by adding whether OAuth feature is enabled and which providers are configured.

close #1165

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.54%. Comparing base (0c15287) to head (51a0245).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1183      +/-   ##
==========================================
+ Coverage   98.52%   98.54%   +0.01%     
==========================================
  Files          40       40              
  Lines        5033     5077      +44     
==========================================
+ Hits         4959     5003      +44     
  Misses         74       74              

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