Adds an activity to the job's timeline, recorded as logged by the token's user. Send it inside an
activity object. activity_type is required; use note, call, email, meeting, sms or
door for touchpoints you log. direction defaults to outbound.

To log something that already happened, send occurred_at (a past date-time, at most a few
minutes ahead of now) and the activity is dated then rather than now. Logging a note, call,
email, meeting, text or door knock can tick off matching steps on the job's checklist.

The token's user must be able to see the job.