refactor: changed client metaprogramming to send with real methods

[maxveldink]

This PR

• adds this new feature

Related Issues

Fixes #1234523

Notes

Follow-up Tasks

How to test

[codecov]

Codecov Report

Attention: Patch coverage is 92.85714% with 2 lines in your changes missing coverage. Please review.

Project coverage is 98.75%. Comparing base (3ca368d) to head (aa098db).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/open_feature/sdk/client.rb	92.85%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #154      +/-   ##
==========================================
- Coverage   99.54%   98.75%   -0.79%     
==========================================
  Files          16       16              
  Lines         218      241      +23     
==========================================
+ Hits          217      238      +21     
- Misses          1        3       +2     

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