Is your feature request related to a problem? Please describe.

When performing a slow backup, restic will use most available bandwidth. This may slow down unacceptably network-related tasks the user may want to accomplish.

Describe the solution you'd like
A feature to pause the upload would allow the user to perform their network-intensive operation, then resume the backup.

Additional context
restic doesn't seem to have a way to pause backups, but users suggested the backup can be interrupted and restarted later with the same effect. Could Backrest provide a "pause" button and do this behind the scenes?