Calendar drag and drop

[kevinpapst]

Description

• added drag and drop support for calendar (recent activities - fixes Improve calendar view with last activities #1852)
• fixes Calendar view font is resulting in unreadable entries #1215 contrast font color
• fixes Calendar popup does not disappear #1448 sticky popover
• fixes Project/Activity color in Calendar view #1946 customer/project/activity colors

Can be tested at https://demo-branch.kimai.org/en/calendar/ with eg. susan_super / kitten and other accounts

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I verified that my code applies to the guidelines (composer code-check)
• I updated the documentation (see here)
• I agree that this code is used in Kimai and will be published under the MIT license

[codecov]

Codecov Report

Merging #1962 into master will increase coverage by 0.04%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1962      +/-   ##
============================================
+ Coverage     93.34%   93.39%   +0.04%     
- Complexity     5325     5430     +105     
============================================
  Files           504      515      +11     
  Lines         16405    16663     +258     
============================================
+ Hits          15313    15562     +249     
- Misses         1092     1101       +9     

Impacted Files	Coverage Δ	Complexity Δ
...rializer/ValidationFailedExceptionErrorHandler.php	100.00% <ø> (ø)	6.00 <0.00> (?)
src/API/TimesheetController.php	96.85% <ø> (+0.42%)	83.00 <0.00> (+1.00)
src/Calendar/Google.php	100.00% <ø> (ø)	3.00 <0.00> (ø)
src/Calendar/GoogleSource.php	100.00% <ø> (ø)	6.00 <0.00> (?)
src/Calendar/RecentActivitiesSource.php	100.00% <ø> (ø)	9.00 <0.00> (?)
src/Calendar/TimesheetEntry.php	100.00% <ø> (ø)	16.00 <0.00> (?)
src/Configuration/CalendarConfiguration.php	100.00% <ø> (ø)	14.00 <0.00> (ø)
src/Configuration/FormConfiguration.php	100.00% <ø> (ø)	11.00 <0.00> (ø)
src/Configuration/SystemConfiguration.php	100.00% <ø> (ø)	16.00 <0.00> (+14.00)
src/Configuration/ThemeConfiguration.php	92.85% <ø> (ø)	7.00 <0.00> (ø)
... and 50 more