Advanced Form Submission - JSON Payload

I am trying to create an advanced form within Sparkle to talk to a CRM. The CRM uses a post to a URL with a required JSON Post payload. Obviously the URL and post isn’t a problem but I cannot find where to add the payload code. Or, perhaps, it is not possible.
Thoughts? Ideas? What am I missing?

Hi @approvedbycharles, welcome.

Sparkle’s post is a regular HTTP post, if you want to call a webservice you need to write some server side code to receive the form, build the JSON and send it to the webservice. Alternatively it could be possible to write some javascript code in an embed element that intercepts the form button click, builds the JSON and sends it directly to the webservice endpoint. It can be a bit more tricky and it depends what you need to do.