Currently, this is making the new message text view pass a callback
to be invoked after it's successfully created, instead of clearing
the text right away, so that if the user declines the creating, they
have the ability to edit their message
just using js/confirm now, which is pretty ugly & page-modal;
should probably actually make some UI for this; would also let us not
block in re-frame.
Pursuant to #199
Some things to still consider: