Stop a campaign permanently, setting its status to stopped (4).

Only a campaign whose status is sending (2) or paused (3) can be stopped. Stopping is not reversible through this endpoint: a stopped campaign cannot be resumed or re-enabled. It also finalizes the campaign's sending state - the outstanding process row is removed and the campaign's sent totals are written from the counts recorded so far.

This endpoint reports business-rule failures in the response body rather than with an
error status: an unknown campaign, an automation ("series") campaign, a completed campaign and a
transition that is not allowed from the campaign's current status all return 200 with succeeded
set to 0. The message text is localized to the account language, so match on succeeded rather
than on the message.