Refactor calendar methods into util class

[rejas]

Refactored some methods in calendar module:

• move methods into own file
• dont call shorten method from titelTransform because why? just call them after each other.
• added tests for util methods
• cleaned up other tests

[codecov-commenter]

Codecov Report

Merging #3088 (ff07366) into develop (dee3cd3) will decrease coverage by 1.88%.
The diff coverage is 66.80%.

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@@             Coverage Diff             @@
##           develop    #3088      +/-   ##
===========================================
- Coverage    27.90%   26.02%   -1.88%     
===========================================
  Files           52       53       +1     
  Lines        11574    11583       +9     
===========================================
- Hits          3230     3015     -215     
- Misses        8344     8568     +224     

Impacted Files	Coverage Δ
modules/default/calendar/calendar.js	0.00% <0.00%> (-34.19%)	⬇️
modules/default/calendar/calendarfetcherutils.js	66.06% <66.06%> (ø)
modules/default/calendar/calendarutils.js	95.83% <96.00%> (+29.76%)	⬆️
modules/default/calendar/calendarfetcher.js	93.08% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[rejas]

would then be ready to merge @khassel :-)