Mechanics Need to Know What Items to Work On

Mechanics have no tie in to this rental system. They are always guessing at which bikes went out. While the hours may go up, they don't indicate the last time a bike was worked on. At a basic level, you could have one additional field on tracked products "hours since last service"; that goes up in tandem with the "hours rented out" field. But, that we can reset to 0 when the bike has been worked on. That way the mechanics know what items to work on, and which they can ignore.