Use req.Body readers to reduce allocs

[michel-laterman]

Pass req.Body directly to decompressGzip in order to remove the allocs an io.ReadAll call creates.

[codecov]

Codecov Report

❌ Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.79%. Comparing base (d508718) to head (67b4b8e).
⚠️ Report is 19 commits behind head on main.

Files with missing lines	Patch %	Lines
server/serverimpl.go	60.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #489      +/-   ##
==========================================
+ Coverage   81.71%   81.79%   +0.07%     
==========================================
  Files          27       27              
  Lines        2122     2131       +9     
==========================================
+ Hits         1734     1743       +9     
  Misses        263      263              
  Partials      125      125              

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[michel-laterman]

The only other alloc reduction I think we should consider is replacing io.ReadAll with something like:

var b bytes.Buffer
_, err := io.Copy(&b, reader)
return b.Bytes(), err

which performs better, but may be over doing it