Remember campaign set of last pausing operation

[baecher]

As an incident responder I would like to be able to resume marketing without having to note down the hash from the pausing operation because I may forget this and accidentally close my terminal.

The most straight forward implementation would be to store the campaign-sets hash of the most recent pausing operation on disk. Running unpause without arguments would take this hash as input.

More sophisticated implementations could later store a structured append-only log similar to git reflog.