Add await when saving data to be sure db is up to date when client will refresh ui

[ip512]

This will fix some edge cases where faircalendar is not refreshed correctly after an event is added

[codecov]

Codecov Report

Merging #192 (64963e6) into master (72e1526) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #192   +/-   ##
=======================================
  Coverage   91.46%   91.47%           
=======================================
  Files         224      224           
  Lines        2719     2721    +2     
  Branches      142      142           
=======================================
+ Hits         2487     2489    +2     
  Misses        232      232           

Impacted Files	Coverage Δ
...ion/FairCalendar/Command/AddEventCommandHandler.ts	100.00% <100.00%> (ø)
...e/Leave/Converter/LeaveRequestToLeavesConverter.ts	96.29% <100.00%> (ø)

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