Backward availability

It's possible to create impossible backward availability, such as:

added Bug label

assigned to @DavePikopPokam

mentioned in issue #160

added Registraton label

Thanks for reporting this. Now, users cannot select an end time earlier than the start time, A popup appears to guide them.

created branch 177-backward-availability to address this issue

mentioned in merge request !39 (merged)

mentioned in commit f5504078

closed with merge request !39 (merged)