[native] Upload video thumbnails to keyserver and persist in serverDB
Summary:
This diff uploads the local thumbnail generated on the native client to the keyserver where the contents will be persisted in the uploads table of the serverDB.
NOTE: This diff can be landed as-is. The entry's container column will be NULL since there's still plenty of work we need to do in multimediaMessageCreationResponder(...) before we're ready to call assignMedia(...) (or the equivalent) to set the container value. However, it's still fine to add these entries to the uploads table because they'll be swept up by the deleteUnassignedUploads (keyserver/src/deleters) cron job that runs every day at 3:30AM PT (keyserver/src/cron/cron.js).
Test Plan:
- Send a video message on native (iOS Simulator)
- Open uploads table in the serverDB (MariaDB)
- Check to see whether there are two rows for the sent media message. One with the contents of the video, and another with the thumbnail image:
Reviewers: abosh, tomek, jacek, ashoat
Reviewed By: abosh, tomek
Differential Revision: https://phab.comm.dev/D4979