Decrement invoice counter

[kevinpapst]

Description

• fix increment for cc, ccy, ccn, ccd (increment was not possible before for these fields)
• added decrement (for configs like {cy-5,3} - eg. when changing the invoice format during the year)
• more tests
• tests for undefined behavior (to document unclear points)
• includes a BC break for undefined, unsupported & undocumented behavior (config like {cy+-1})

Documentation: kimai/www.kimai.org#75

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 #1947 into master will increase coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #1947   +/-   ##
=========================================
  Coverage     93.39%   93.39%           
- Complexity     5430     5437    +7     
=========================================
  Files           515      515           
  Lines         16663    16682   +19     
=========================================
+ Hits          15562    15580   +18     
- Misses         1101     1102    +1     

Impacted Files	Coverage Δ	Complexity Δ
...ce/NumberGenerator/ConfigurableNumberGenerator.php	97.93% <ø> (-0.78%)	32.00 <0.00> (+7.00)	⬇️