Adding polygon and json fields to save

I have several components working but we're finding one component needs to be updated. This requires adding two fields, type of 'polygon' and a type JSON

The way it would work is:

1. The view outputs the form and a google map (working)
2. The user fills in the form and draws a polygon on that map (working)
3. The polygon points (latitudes and longitudes) are stored in a hidden form as a JSON string (easy enough)
4. The user clicks save
5. The form is validated
6. The save occurs

I need to catch/modify the save (#6) so I can unpack the JSON string, put the points together into something like this:
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When the model returns the data, it only needs to return the JSON into a hidden form var. If it exists, I'll unpack that and redraw the polygon on the map. I think I have this figured out but not 100% certain.

I've figured out how to upgrade the table. That's not a problem.

So my questions are:

1. How/where do I modify the component to add the json field so that it saves?
2. How/where do I intercept the save process so that I can extract the JSON points and create the POLYGON entry?

Thanks!