json fields enclosed in quotes when form does not validate

I believe it is somewhat related with https://github.com/ckan/ckanext-scheming/pull/165

If the dataset creation form does not validate, my json fields are enclosed in double-quotes. If it fails validating a seconde time, those double-quotes are escaped and it is enclosed in another set of double-quotes, etc.

For instance, leaving on-purpose some mandatory fields empty so I get a validation error, my geojson field, initially set at
`
{"type": "Polygon", "coordinates": [[[-1.791023, 42.777538], [-1.791023, 47.175876], [2.611496, 47.175876], [2.611496, 42.777538], [-1.791023, 42.777538]]]}
`
becomes
`
"{\"type\": \"Polygon\", \"coordinates\": [[[-1.791023, 42.777538], [-1.791023, 47.175876], [2.611496, 47.175876], [2.611496, 42.777538], [-1.791023, 42.777538]]]}"
`
And after failing again to validate my form, would become on 2nd step:
`
"\"{\\\"type\\\": \\\"Polygon\\\", \\\"coordinates\\\": [[[-1.791023, 42.777538], [-1.791023, 47.175876], [2.611496, 47.175876], [2.611496, 42.777538], [-1.791023, 42.777538]]]}\""
`
This is obviously not json-valid anymore...

Reproduce the dataset creation form failure using the geojson field and the example value in the issue, submitting it repeatedly to observe the quoting. Read the related ckanext-scheming pull request 165 for context. Done means the field remains valid JSON after validation errors and repeated submissions.

Written by the indexing model from the issue text.