feat!: enhance credentials usage and update warning message for credentials requests

[jeevatkm]

• User type become unexported
• HTTP not secure warning message added for auth token flow too
• Intialize the default auth scheme value Bearer during client creation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.11%. Comparing base (f18ee43) to head (9a568fc).
Report is 12 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #915      +/-   ##
==========================================
+ Coverage   98.79%   99.11%   +0.32%     
==========================================
  Files          15       15              
  Lines        3230     3285      +55     
==========================================
+ Hits         3191     3256      +65     
+ Misses         28       20       -8     
+ Partials       11        9       -2     

Flag	Coverage Δ
unittests	99.11% <100.00%> (+0.32%)	⬆️

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