Add reasoning effort parameter to OpenAI Spec ChatCompletionRequest

[bhimrazy]

What does this PR do ?

Fixes #547

Introduce a new reasoning_effort field to the ChatCompletionRequest model and implement corresponding tests to validate its functionality in the API responses.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85%. Comparing base (1ca73c5) to head (73661f0).
Report is 1 commits behind head on main.

Additional details and impacted files

@@         Coverage Diff         @@
##           main   #548   +/-   ##
===================================
  Coverage    85%    85%           
===================================
  Files        38     38           
  Lines      2901   2902    +1     
===================================
+ Hits       2479   2480    +1     
  Misses      422    422           

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