Implement test for ECR multi-arch image and fix possible content length missing

[jonesbusy]

Only partial fix for #514

Description

Add test for public ECR public registry (failing for now) to demonstrate issue #514

Fix possible null content length that might not be present on reponse

Testing done

mvn clean install

Submitter checklist

• I have read and understood the CONTRIBUTING guide
• I have run mvn license:update-file-header, mvn spotless:apply, pre-commit run -a, mvn clean install before opening the PR

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.14%. Comparing base (f248237) to head (1694d3e).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #515      +/-   ##
============================================
+ Coverage     87.25%   88.14%   +0.88%     
- Complexity      653      654       +1     
============================================
  Files            39       39              
  Lines          2001     2007       +6     
  Branches        226      227       +1     
============================================
+ Hits           1746     1769      +23     
+ Misses          162      145      -17     
  Partials         93       93              

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