added username to export

[kevinpapst]

Description

Fixes #1823

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 #1827 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             master    #1827   +/-   ##
=========================================
  Coverage     92.36%   92.37%           
- Complexity     5064     5068    +4     
=========================================
  Files           471      471           
  Lines         15670    15680   +10     
=========================================
+ Hits          14474    14484   +10     
  Misses         1196     1196           

Impacted Files	Coverage Δ	Complexity Δ
src/Export/Base/AbstractSpreadsheetRenderer.php	91.28% <100.00%> (+0.31%)	115.00 <0.00> (+4.00)