Using http://requestb.in I have figured out that Forms "Webhook" simply sends a request that looks like this:
{"bpInstanceId":13,"submissionId":19}
I am assuming that now I need to somehow have the third-party app send back a similar HTTP POST to Forms, saying "Okay, send me all the variables for bpInstanceId 13" similar to the way that Workflow makes this request in a "Retrieve Laserfiche Forms Content" activity.
Is there documentation that shows how to make this request of the Forms service?