Custom widgets/validation?

Copied from kinto/kinto#1083.

You can specify a schema for your data, and a uiSchema for how to build the form for it. I'd like to be able to add a custom type for a field (specifically, a JEXL expression) that has custom validation, and potentially a UI widget that helps in writing that custom type.

But that custom type doesn't seem like a thing I should, say, land in Kinto itself. I'd like to be able to write something like a plugin for Kinto that adds support for my new custom type to a Kinto instance. I dunno if that's already possible or how hard it would be to add, though.

Thanks!

Start by inspecting how schema and uiSchema are handled in the admin console and whether Kinto instances already expose a plugin or extension entry point. Determine whether custom field types can provide validation and an optional form widget, then document the supported integration path and verify it with a representative custom type such as a JEXL expression.

Written by the indexing model from the issue text.