Add Documentation for proxy failure modes

[AndreKurait]

Description

Add Documentation for proxy failure modes

• Category: Documentation
• Why these changes are required? Give a starting point for specifying failure cases in the proxy to educate users around behaviors and configuration
• What is the old behavior before changes and new behavior after changes? No functional change

Issues Resolved

MIGRATIONS-1487

Is this a backport? If so, please add backport PR # and/or commits #

Testing

Viewed README in markdown viewer

Check List

• [ x] New functionality includes testing
  • [ x] All tests pass, including unit test, integration test and doctest
• [x ] New functionality has been documented
• [x ] Commits are signed per the DCO using --signoff

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[gregschohn]

I think that this is a good start. I'd love to add a column to this table to reference a line of code for the test that shows that these behaviors are being tested.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.02%. Comparing base (384401e) to head (987125c).
Report is 9 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #595      +/-   ##
============================================
+ Coverage     75.91%   76.02%   +0.11%     
- Complexity     1491     1494       +3     
============================================
  Files           162      162              
  Lines          6348     6348              
  Branches        572      572              
============================================
+ Hits           4819     4826       +7     
+ Misses         1152     1145       -7     
  Partials        377      377              

Flag	Coverage Δ
unittests	76.02% <ø> (+0.11%)	⬆️

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