Content negotiation: Enable override of chosen media type when Accept header is missing

[bkoelman]

We need this to workaround a bug in NSwag: its generated client doesn't send an Accept header when only error responses define a content type.

QUALITY CHECKLIST

• Changes implemented in code
• Complies with our contributing guidelines
• N/A: Adapted tests
• N/A: Documentation updated

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.68%. Comparing base (0c79d35) to head (9573731).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1644   +/-   ##
=======================================
  Coverage   90.68%   90.68%           
=======================================
  Files         353      353           
  Lines       11514    11515    +1     
  Branches     1897     1898    +1     
=======================================
+ Hits        10441    10442    +1     
  Misses        702      702           
  Partials      371      371           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.