SQS: Support JSON format

[bblommers]

Fixes #6286

[codecov]

Codecov Report

Merging #6331 (d68b03a) into master (523225d) will decrease coverage by 0.12%.
The diff coverage is 61.34%.

@@            Coverage Diff             @@
##           master    #6331      +/-   ##
==========================================
- Coverage   96.28%   96.16%   -0.12%     
==========================================
  Files         792      793       +1     
  Lines       77067    77397     +330     
==========================================
+ Hits        74203    74429     +226     
- Misses       2864     2968     +104     

Flag	Coverage Δ
servertests	36.90% <32.35%> (-0.05%)	⬇️
unittests	96.10% <61.34%> (-0.12%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
moto/core/exceptions.py	95.83% <25.00%> (-4.17%)	⬇️
moto/sqs/responses.py	78.06% <59.04%> (-17.94%)	⬇️
moto/sqs/models.py	96.08% <66.66%> (-0.14%)	⬇️
moto/sqs/utils.py	96.00% <88.23%> (+0.65%)	⬆️
moto/utilities/constants.py	100.00% <100.00%> (ø)

... and 6 files with indirect coverage changes

[github-actions]

This is now part of moto >= 4.1.11.dev7