Unit Test and Refactor NATs Publisher

[rossnelson]

• Introduced Logger interface and added logging to CircuitBreaker
• Refactored Config to include Logger
• Updated validateConfig to set default Logger if nil
• Added Breaker and JetStream interfaces
• Refactored Connector interface and related implementations
• Updated unit tests to mock new interfaces and logging

[codecov]

Codecov Report

Attention: Patch coverage is 91.30435% with 4 lines in your changes missing coverage. Please review.

Project coverage is 51.69%. Comparing base (f9856c5) to head (098db6e).
Report is 1 commits behind head on main.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
circuitbreaker/circuitbreaker.go	88.88%	2 Missing and 1 partial ⚠️
messaging/natsjspub/natsjspub.go	93.75%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #52      +/-   ##
==========================================
+ Coverage   50.12%   51.69%   +1.57%     
==========================================
  Files         126      126              
  Lines        4986     5002      +16     
==========================================
+ Hits         2499     2586      +87     
+ Misses       2349     2272      -77     
- Partials      138      144       +6     

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