Restore billing for a session whose billing was dropped, returning it to suspended billing. The action runs as the
token owner, who is recorded on the session edit log and on the action audit record.

Requires the Sessions.resume-billing permission - a token whose admin does not hold it is rejected with 403, and so
is a request for a session that belongs to another operator. An unknown session ID is rejected with 404.

Preconditions, with the response code each failure produces. A temporary lock takes precedence over a session-state conflict:

• No recalculation is running for the session and the session is not locked for billing processing - otherwise 423
• billingStatus is dropped - otherwise 409
• reason is at most 1000 characters - otherwise 422

The action ends with billingStatus set to suspended. Nothing is billed and the validation rules are not re-run.
Use the Session / Resume billing action afterwards to bill the session, mark it as free or drop it again.