Switch client CLI to argparse

[johnpaulett]

Summary

• migrate from optparse to argparse in hl7.client
• update unit tests for argparse

Testing

• pytest -q

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https://chatgpt.com/codex/tasks/task_b_68436781a594832791e684f24dd3933a

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.17%. Comparing base (b2a32c1) to head (1611c1d).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #68      +/-   ##
==========================================
+ Coverage   89.81%   90.17%   +0.35%     
==========================================
  Files          20       20              
  Lines        1610     1618       +8     
  Branches      233      233              
==========================================
+ Hits         1446     1459      +13     
+ Misses        117      113       -4     
+ Partials       47       46       -1     

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