Various code improvements

[opatry]

Description

• Cover API contract checks (invalid arguments)
• Remove invalid TODO for menu section title
• Remove enableMoveToList feature flag, we can always move a task to another list even when 1 list only
• Rename Task.asTaskEntity parameters for clarity
• Print TaskRepository tree when a test fails
• Fix InMemoryTasksApi not replacing existing content properly

Checklist

• I have read the CONTRIBUTING guide
• Code compiles correctly
• Created tests which fail without the change (if possible)
• All tests passing