Resolve "Expired but unclaimed time slots still apear."

What does this MR do?

Time slots that were expired but not claimed were still shown in the list of available time slots for a guest.

Actions taken to fix the bug

The time slots are now also filtered on the time, instead of only on claimed/unclaimed.

Does this MR meet the acceptance criteria?

• I have added tests to validate the fix.
• I have updated the documentation accordingly.
• I have added translations for all new client-side text. Closes #147 (closed)