Fix Datepicker localization

[georgehrke]

fixes #2174

fixes first day of week
fixes title of month in header

Before	After

[codecov]

Codecov Report

Merging #2286 into master will decrease coverage by 0.04%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##             master    #2286      +/-   ##
============================================
- Coverage     27.64%   27.60%   -0.05%     
  Complexity      103      103              
============================================
  Files           144      145       +1     
  Lines          5288     5297       +9     
  Branches        798      798              
============================================
  Hits           1462     1462              
- Misses         3826     3835       +9     

Flag	Coverage Δ	Complexity Δ
#javascript	22.23% <0.00%> (-0.05%)	0.00 <0.00> (ø)
#php	94.41% <ø> (ø)	103.00 <ø> (ø)

Impacted Files	Coverage Δ	Complexity Δ
src/components/Shared/DatePicker.vue	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
src/components/Shared/TimePicker.vue	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
src/utils/localization.js	0.00% <0.00%> (ø)	0.00 <0.00> (?)

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[georgehrke]

src/utils/localization.js still needs some tests, once i added them this is ready to test.

It's a pain to test with mocking moment, will have to find a more elegant solution later.

[tcitworld]

Didn't have a look yet but from the screenshot short day of week names are not localized.

[georgehrke]

Didn't have a look yet but from the screenshot short day of week names are not localized.

The days names in the screenshot are correctly localised in german:
(Mo)ntag (Di)enstag (Mi)ttwoch ...

[tcitworld]

I thought that was French. :p

[dnv]

Is this getting fixed? My Nextcloud locale is set to English (Finland) with Week starts on Monday clearly shown under Settings, yet the Calendar week starts on Sunday when opened via web browser.

[tcitworld]

@dnv See #2663