Add test that demonstrates the status bug

[grcevski]

In this testcase we have a Go middleware that has its own implementation of ResponseWriter, which in turn stores the statusCode in it's own field.

I didn't add an integration test yet because it will fail.

Relates to #202

[codecov-commenter]

Codecov Report

Merging #204 (474d63d) into main (8aac953) will decrease coverage by 40.80%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             main     #204       +/-   ##
===========================================
- Coverage   81.23%   40.43%   -40.80%     
===========================================
  Files          35       34        -1     
  Lines        2697     2641       -56     
===========================================
- Hits         2191     1068     -1123     
- Misses        373     1510     +1137     
+ Partials      133       63       -70     

Flag	Coverage Δ
integration-test	?
unittests	40.43% <ø> (ø)

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see 27 files with indirect coverage changes

[grcevski]

Thanks Mario!