Get an invocation with its jobs and tasks

Returns an invocation attempt together with every job definition, its latest job run, and the task definitions and active task runs of that job run. Defaults to the latest attempt when attempt is omitted. With follow=1 the response is a newline-delimited JSON stream: a {"type":"tree", ...} event with the full tree is sent immediately and again whenever it changes, and a final {"type":"end","reason":...} event is sent when the attempt finishes (completed) or the stream reaches its maximum duration (timeout), after which clients should reconnect.