test: add httparse tests and make errors identical

[jbr]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 86.66667% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 52.59%. Comparing base (7002c48) to head (b78a290).

Files	Patch %	Lines
http/src/conn.rs	83.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            0.3.x     #653      +/-   ##
==========================================
+ Coverage   52.52%   52.59%   +0.07%     
==========================================
  Files         198      198              
  Lines        7524     7531       +7     
==========================================
+ Hits         3952     3961       +9     
+ Misses       3572     3570       -2     

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