Make fetching HttpClient optional from context in PKCE auth flow

[pmahindrakar-oss]

Tracking issue

Describe your changes

Previous PR introduced authentication with proxy http Client but it added a hard dependency to fetch this from the context .
This causes regression in cases the context is not set with this object.

Current change makes it backward compatible by using the default http client in case the context is not set with it.

Check all the applicable boxes

Tested this change locally by pulling this commit as saw authentication working fine in the broken environments

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

Screenshots

Note to reviewers

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (4fc4988) 58.73% compared to head (8598033) 78.96%.

❗ Current head 8598033 differs from pull request most recent head 2a061f7. Consider uploading reports for the commit 2a061f7 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #4295       +/-   ##
===========================================
+ Coverage   58.73%   78.96%   +20.23%     
===========================================
  Files         583       18      -565     
  Lines       50331     1298    -49033     
===========================================
- Hits        29562     1025    -28537     
+ Misses      18396      209    -18187     
+ Partials     2373       64     -2309     

Flag	Coverage Δ
unittests	?

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Files	Coverage Δ
...dl/clients/go/admin/pkce/auth_flow_orchestrator.go	66.00% <100.00%> (ø)

... and 600 files with indirect coverage changes

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[eapolinario]

Thanks for adding the unit test.