Structured JSON Type Hints

[joornby]

I was recently working on trying to build a plugin to a third party platform that provides their own widget. Upon the user selecting an item in this widget, it provides an event back to the custom admin component I was rendering. What I wanted to do was specify the type of the field as json, and save the information coming back from the third party widget in the field. That would work great, but the format of the data is always the same, so I felt like the generated types and schemas should know the specific shape of the items selected from the widget. I ended up using the group field specifying all of the sub-fields, but the things I had to do to get that to work was pretty ridiculous. So my proposal is that there be a way to define the schema for a json field. There are three primary benefits of allowing a strict type on the json field:

1. Third party widget plugin implementations.
2. The schema that could be used to generate the types could also be passed to the monaco editor instance so that the built in json code editor could provide validation and intellisense aid for content creators using Payload.
3. The generated types and graphql schema make it much simpler to consume JSON data, especially when you know that it's always going to be of a particular shape.