[#2925] Add fixture for samenwerkingen

[pi-sigma]

Closes #2925

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.98%. Comparing base (bb8ad50) to head (40c6051).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #2934   +/-   ##
========================================
  Coverage    93.98%   93.98%           
========================================
  Files         1332     1332           
  Lines        57525    57525           
========================================
  Hits         54065    54065           
  Misses        3460     3460           

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[swrichards]

@pi-sigma this looks good to me, but it would be good to also have a few Berichten in the chat history, would that be possible?