add support for weekly invoice

[maarten-k]

Description

Should close invoice: sum calculation on entry per week
#1434

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)

Checklistcomposer kimai:code-check

• 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

[kevinpapst]

Thanks @maarten-k - I will give it a try soon

[maarten-k]

Documentation can be found at kimai/www.kimai.org#65

[codecov]

Codecov Report

Merging #1780 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             master    #1780   +/-   ##
=========================================
  Coverage     92.30%   92.30%           
- Complexity     4892     4894    +2     
=========================================
  Files           450      451    +1     
  Lines         15136    15142    +6     
=========================================
+ Hits          13971    13977    +6     
  Misses         1165     1165           

Impacted Files	Coverage Δ	Complexity Δ
src/Invoice/Calculator/WeeklyInvoiceCalculator.php	100.00% <100.00%> (ø)	2.00 <2.00> (?)
...rc/Invoice/Hydrator/InvoiceItemDefaultHydrator.php	98.73% <100.00%> (+0.03%)	13.00 <0.00> (ø)

[kevinpapst]

Thank you @maarten-k 👍