Function forget_room_handler 

async fn forget_room_handler(
    room_server: RoomServerConnection,
    __arg1: AuthenticatedClientRequest<Request>,
) -> Result<ArminiusResponse<Response>, ErrorOf<ForgetRoom>>

Handler for POST /_matrix/client/v3/rooms/{roomId}/forget (See https://spec.matrix.org/v1.14/client-server-api/#post_matrixclientv3roomsroomidforget).

This endpoint is used to mark room as forgotten, and ready for deletion