add a i18n api field for the users "now" datetime

[kevinpapst]

Description

Partially solves #1949

Added new field now:

API result:

{
    "formDateTime": "yyyy-MM-dd HH:mm",
    "formDate": "yyyy-MM-dd",
    "dateTime": "m-d H:i",
    "date": "Y-m-d",
    "time": "H:i",
    "duration": "%h:%m h",
    "is24hours": true,
    "now": "2020-10-01T05:02:11+1200"
}

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 #2007 into master will increase coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #2007   +/-   ##
=========================================
  Coverage     93.38%   93.38%           
- Complexity     5461     5462    +1     
=========================================
  Files           516      516           
  Lines         16762    16766    +4     
=========================================
+ Hits          15653    15657    +4     
  Misses         1109     1109           

Impacted Files	Coverage Δ	Complexity Δ
src/API/ConfigurationController.php	100.00% <ø> (ø)	3.00 <0.00> (ø)
src/API/Model/I18nConfig.php	100.00% <ø> (ø)	8.00 <0.00> (+1.00)