Motivation
----------
We were often swallowing errors or yielding generic errors when it would
be better to provide specific errors.
We also didn't create an attachment when attachments failed to send,
making it impossible to show the user what was happening with an
in-progress or failed attachment.
Primary Changes
---------------
- Funnel all message sending through MessageSender, and remove message sending
from MessagesManager.
- Record most recent sending error so we can expose it in the UI
- Can resend attachments.
- Update message status for attachments, just like text messages
- Extracted UploadingService from MessagesManager
- Saving attachment stream before uploading gives uniform API for send vs.
resend
- update status for downloading transcript attachments
- TSAttachments have a local id, separate from the server allocated id
This allows us to save the attachment before the allocation request. Which is
is good because:
1. can show feedback to user faster.
2. allows us to show an error when allocation fails.
Code Cleanup
------------
- Replaced a lot of global singleton access with injected dependencies to make
for easier testing.
- Never save group meta messages. Rather than checking before (hopefully) every
save, do it in the save method.
- Don't use callbacks for sync code.
- Handle errors on writing attachment data
- Fix old long broken tests that weren't even running. =(
- Removed dead code
- Use constants vs define
- Port flaky travis fixes from Signal-iOS
// FREEBIE
