Solo appt

I don't know if it was intentional, but a mentor can have multiple availabilities with the same start time. I added a validation to prevent this. It does not prevent you from sandwiching availabilities (10-12pm and 11-1130pm are valid). But at least this way if you create a second availability (because you may have forgotten about it like I did), it won't duplicate. Then you don't have to go through the email to get the management link.

Also added a flash msg upon creation.