Allow/Create pop ups with reasons why an error

When someone attempts to signup/make reservation the system should say REASON why the error message. Not use "user not allowed". For example, we can make reseravtions 10 days in advance from time. Today someone tried to reserve a 9:30am court at 7:30am 10 days out (too early) but the error is generic. This creates a whole trickle of chaos. If it would say, reservation is too early then it would solve so many admin issues for directors.  Same with events, etc.