POST /api/chat/rooms/{roomId}/typing

Wire body for POST /api/chat/rooms/{roomId}/typing, the relay that lets a process outside netcore raise and lower the visitor's typing indicator. accountId and departmentId travel as query parameters, so the body carries only the flag.

Wire response for the typing relay. sent is a DIAGNOSTIC, not a delivery guarantee: the relay computes it from its own reads of the connection room and the account's connections, taken around the hub call rather than inside it, because the hub method reports no recipient count.