feat: Copy start date to end date when valid
feat: Copy start date to end date when valid

A new feature was developed to copy the valid date from start date
and time to end date and time if:
- the end field is empty
- the end field date is invalid
- the end field date has been set before start date and the start
date has changed

rszczypka/swd-p1-meetup,rszczypka/swd-p1-meetup