INVOICE: do not use activity name as fallback for description

[kevinpapst]

Description

Currently an empty description in a timesheet (and expense) causes Kimai to inject the activity name as invoice variable entry.description in the default calculator (one row per entry).

This makes it impossible to detect whether the description was set or not and apply custom fallback logic.

This was removed: the field entry.description contains now the content from the timesheet. If empty then this field is empty as well.

A replacement field was added called entry.description_safe which will use the activity name as fallback and if that is empty the project name.

This is technically both a bug fix and BC break.

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 (see license)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.75%. Comparing base (e29ef25) to head (ef671c4).

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #4884   +/-   ##
=========================================
  Coverage     87.75%   87.75%           
+ Complexity     8975     8973    -2     
=========================================
  Files           797      797           
  Lines         29431    29428    -3     
=========================================
- Hits          25828    25826    -2     
+ Misses         3603     3602    -1     

Files	Coverage Δ
...rc/Invoice/Calculator/AbstractMergedCalculator.php	92.10% <ø> (-0.40%)	⬇️
...rc/Invoice/Hydrator/InvoiceItemDefaultHydrator.php	100.00% <100.00%> (+1.01%)	⬆️