Datepicker issues

[Yelinz]

When trying to manually write a date, the input field bugs out and doesn't set the written date but a completely different one.

This behavior is caused by us using formatDate without changing the default dateFormat. Because the default format is Y-m-d you can enter dates in that format, but trying to write dates in the displayed way doesn't work.

Either we provide a probably configurable dateFormat which then allows typed input or completely disable typed input

[Yelinz]

If a date is ever set, you can never clear it.

When deleting text out of the date picker, it doesn't trigger the onChange action We would need an icon button in the input box probably, which calls the clear() function of a flatpickr instance. The documentation references this https://shipshapecode.github.io/ember-flatpickr/docs/usage#ember-flatpickr-and-external-elements