implement background message sending in the inbox. when sending any
message, the form now unlocks right away and a progress bar appears
at the top. you can potentially have several messages sending at once,
each with its own progress bar. determinate progress bars (i.e. for
bulk private messages) will still be on the page if you reload (assuming
they haven't finished sending).
also implement client-side form validations so that users are prompted to
put in recipients and a message
progress bar should be aria compliant. refs #9237
test plan:
1. send a new message to a single recipient
2. there should be an indeterminate progress bar as it sends, and the ui
should be unlocked
3. send a new group message
4. see step 2.
5. send a bulk private message
6. there should be a determinate progress bar as it sends, and it should
move with a relatively consistent velocity. the ui should be unlocked
7. send a message on an existing conversation
8. see step 2.
9. repeat steps 1-8 with attachments
10. try sending messages without a body or recipients. you should get red
error boxes
Change-Id: I1e4641505c3e4c42f840b292d739c78cb1c2baff
Reviewed-on: https://gerrit.instructure.com/13617
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Zach Pendleton <zachp@instructure.com>
308bebe454
