CalendarObjectInstance: reset attendee participation status on duplication of an event

[GVodyanov]

Fix #5793

That eventComponent is black magic...

[codecov]

Codecov Report

Attention: Patch coverage is 20.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 23.75%. Comparing base (cbfbda2) to head (0b7f8dc).
Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
src/models/event.js	25.00%	2 Missing and 1 partial ⚠️
src/store/calendarObjectInstance.js	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6302      +/-   ##
============================================
- Coverage     23.76%   23.75%   -0.01%     
  Complexity      454      454              
============================================
  Files           246      246              
  Lines         11715    11718       +3     
  Branches       2207     2220      +13     
============================================
  Hits           2784     2784              
- Misses         8614     8615       +1     
- Partials        317      319       +2     

Flag	Coverage Δ
javascript	15.35% <20.00%> (-0.01%)	⬇️
php	59.53% <ø> (ø)

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[ChristophWurst]

can we haz backport?

[GVodyanov]

/backport to stable5.0