Resume one paused campaign.

Only a paused campaign of this account can be resumed. On a paid account, resuming sends nothing by itself: the steps held while it was paused go out through the normal schedule, inside the send window and the daily caps. A step whose time passed while paused goes out at the next allowed slot, one step at a time per lead — the step after it still waits its own delayDays from when that one actually sent, so a pause never puts two steps in one day. Leads stopped on their own stay stopped: stopped with pause leadEmails, replied, unsubscribed, bounced or suppressed.