Warn the user when labor students are volunteering for a service event

In order to avoid the situation where a CELTS labor student earns service hours for an event where they are working, we should have a warning message in kiosk mode when a student who is currently a labor student with CELTS scans in to an event that earns service hours.

We are implementing the ability to scan in as either a labor student or a volunteer, and the message should only be displayed if they have scanned in as a volunteer. If this feature is not complete at the time this issue is worked on, the message can display when anyone scans in.

Use the other service hour warnings we have as a basis for the text of this message.