Rails automatically disables buttons when submitting a form. This works
fine most of the time: for AJAX requests, it enables them again after
the request is complete, and for non-AJAX requests, the button is
replaced by a new element when the new page loads.
However, there's an exception. When a request returns data so users can
download a fire, the request is not an AJAX one and the button is not
replaced. So users are left with a disabled button they can no longer
click.
So in this case, we aren't disabling the button after a user clicks it.
Why:
Newsletter attribute `segment_recipient` is an integer to be used as
enum. There's no advantage to store a number instead of an string if the
ammount of elements in the table is not going to be huge, or we can take
advantage of using an enum.
Also maintaining both Newsletters enum paired with UserSegments::SEGMENTS
would be a maintenance burden.
How:
* Migration to change segment_recipient column from integer to string
* Removing enumeration from Newsletter model class
* Using UserSegments::SEGMENTS instead of Newsletter.segment_recipients
or integer values
