DM-38599: Fix contents length checking in server-encoded HTTP responses

[airnandez]

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes

[codecov]

Codecov Report

Patch coverage: 33.33% and project coverage change: -0.03 ⚠️

Comparison is base (1b3121a) 85.49% compared to head (004c49b) 85.47%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #51      +/-   ##
==========================================
- Coverage   85.49%   85.47%   -0.03%     
==========================================
  Files          27       27              
  Lines        3731     3732       +1     
  Branches      766      767       +1     
==========================================
  Hits         3190     3190              
  Misses        428      428              
- Partials      113      114       +1     

Impacted Files	Coverage Δ
python/lsst/resources/http.py	81.03% <33.33%> (-0.15%)	⬇️

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[timj]

Looks okay. I don't think the two length variable definitions needed to move but I'm also fine with them in the new location.