Notifications by SweetAlert2

[kevinpapst]

Description

Currently Kimai uses two ways of showing user feedback:

• SweetAlert2 mostly for API and AJAX calls
• In page errors and success messages after form submission

This PR changes that behavior: all notifications will be rendered by SweetAlert => no more "jumping pages".

Open question
sweetalert2 cannot display multiple messages at once => how should that be handled?

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 kimai: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 #1508 into master will decrease coverage by 0.05%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1508      +/-   ##
============================================
- Coverage     93.38%   93.32%   -0.06%     
- Complexity     5461     5465       +4     
============================================
  Files           516      516              
  Lines         16762    16772      +10     
============================================
  Hits          15653    15653              
- Misses         1109     1119      +10     

Impacted Files	Coverage Δ	Complexity Δ
src/Controller/AboutController.php	61.53% <ø> (-5.13%)	4.00 <0.00> (ø)
src/Controller/AbstractController.php	64.86% <ø> (-20.85%)	18.00 <0.00> (+4.00)	⬇️
src/Controller/ActivityController.php	92.44% <ø> (ø)	42.00 <0.00> (ø)
src/Controller/CustomerController.php	91.24% <ø> (ø)	52.00 <0.00> (ø)
src/Controller/HomepageController.php	76.19% <ø> (-3.81%)	5.00 <0.00> (ø)
src/Controller/InvoiceController.php	79.88% <ø> (+0.45%)	52.00 <0.00> (ø)
src/Controller/PermissionController.php	92.72% <ø> (ø)	27.00 <0.00> (ø)
src/Controller/ProjectController.php	91.47% <ø> (ø)	55.00 <0.00> (ø)
src/Controller/SystemConfigurationController.php	98.57% <ø> (ø)	22.00 <0.00> (ø)
src/Controller/TagController.php	89.23% <ø> (ø)	16.00 <0.00> (ø)
... and 9 more