Add more tests for calendar contribution

What does this MR do?

Add more tests for calendar contribution

Are there points in the code the reviewer needs to double check?

Shouldn't be

Why was this MR needed?

Improve test coverage for calendar

Screenshots (if relevant)

None

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #22347 (closed)