Sync new RSVPs from AK to VAN [3]

[aguestuser]

Acceptance criteria

GIVEN a running job polling for new AK events and a way to write to VAN:

• WHEN the server retrieves a new record (event, person, rsvp) from ActionKit
• THEN it will check to see if it has already synced each record
• AND then push all unsynced records to VAN

Implementation Notes

• we can tell if we have already synced a record if (1) we have both AK & VAN ids
• don't ever delete RSVP's (if that's even possible)

Dependencies

• depends on Listen for new RSVPs in ActionKit [3] #1 and Create new RSVPs in VAN [3] #2