feat: omit content-type header when no parameters are present

[tangcent]

close #1167

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.744%. Comparing base (bf67a5c) to head (5e9c24c).
Report is 1 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff               @@
##              master     #1169       +/-   ##
===============================================
- Coverage     62.756%   62.744%   -0.012%     
+ Complexity      2374      2373        -1     
===============================================
  Files            255       255               
  Lines          12335     12331        -4     
  Branches        3030      3029        -1     
===============================================
- Hits            7741      7737        -4     
  Misses          3009      3009               
  Partials        1585      1585               

Flag	Coverage Δ
unittests	62.744% <ø> (-0.012%)	⬇️

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Files with missing lines	Coverage Δ
...dea/plugin/api/export/core/RequestClassExporter.kt	60.412% <ø> (-0.359%)	⬇️

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