Set the resulting metadata ID after creating a backup.
Refactor backups metadata storage to use an external session.
Use a new backups for each API request (and close when finished).
Switch backups archive storage to gridfs.
Run -> RunTransaction.
NewBackupsStorage -> NewBackupStorage.
Store backups data/metadata in a separate mongo database.
Use a DB info struct with information about which databases to dump.
Build the backup dump info from juju state.
Dump each database separately.
Explicitly identify the auth DB.
Drop the --oplog option.