Adds support for multiple attendees in the data-attendee field and changes name to attendees to reflect this.
Changes get_attendee_id to get_attendee_ids to support multiple attendees.
Removes unnecessary setting of user_id.
Makes spinner show when AJAXing the slot assignment.
Removes extra whitespace.
Removes spare debugging.
Adds blocking div on the UI if the field is marked unavailable on page load.
Adds support for cancelling unavailability in slots
Removes extra logging
Ensures that all values are treated as strings to avoid errors.
Removes debugging and tidies up...
Add checks for new attendees format data.