Fix proxy_context_path does not work as expected in authorize request

[deshankoswatte]

Proposed changes in this pull request

• Introduced a new configuration property OAuth.UseAbsolutePublicURLForAuthRequest to control whether the commonAuthCallerPath is built using the absolute public URL or the relative internal URL.
• Updated EndpointUtil to use ServiceURLBuilder and select between getAbsolutePublicURL() and getRelativeInternalURL() based on the config.
• This allows deployments that require the absolute public URL in the authorize request flow to work correctly.
• The configuration is as follows:

[oauth]
use_absolute_public_url_for_auth_request = false

Fixes: wso2/product-is#22673, wso2/product-is#25357.

When should this PR be merged

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Follow up actions

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[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 57.72%. Comparing base (3382285) to head (b10856f).
⚠️ Report is 202 commits behind head on master.

Files with missing lines	Patch %	Lines
...bon/identity/oauth/endpoint/util/EndpointUtil.java	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2870      +/-   ##
============================================
- Coverage     57.72%   57.72%   -0.01%     
+ Complexity     8989     8970      -19     
============================================
  Files           668      668              
  Lines         50067    50070       +3     
  Branches      10854    10855       +1     
============================================
+ Hits          28901    28902       +1     
+ Misses        17152    17151       -1     
- Partials       4014     4017       +3     

Flag	Coverage Δ
unit	40.09% <75.00%> (-0.01%)	⬇️

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