Runs model

[taylordowns2000]

Create runs model using a generator.

started_at
finished_at
exit_code
log
job_id
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message_id // initial_state (???) // source // [ input ]
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triggering_event

triggering_event samples:

{ "type": "webhook", "state": {"data": {a:1} } }, // this is an event that's generated/captured from an external system 
{ "type": "cron", "state": {"cursor" :123 } } // this is an event that's generated by the `cron_service`

From BPMN: A Process (JOB) can be executed or performed many times, but each time is expected to follow the steps laid out in the Process model (JOB EXPRESSION, OPERATIONS). For example, the Process in Figure 10.1 will occur every Friday, but each instance (RUN) is expected to perform Task “Receive Issue List,” then Task “Review Issue List,” and so on, as specified in the model. Each instance (RUN) of a Process is expected to be valid for the model, but some instances might not, for example if the Process has manual Activities, and the performers have not had proper instruction on how to carry out the Process.