Remove $ref restriction

[flying-sheep]

I can’t find a reason why you block $ref from being used.

Using $ref with https URLs can be safe, and using it with relative paths definitely is.

Is there any still applicable reason the restriction is still in place?

[birnbera]

+1 for this, however, I'd be happy with at least allowing the default $ref implementation in jsonschema, which allows schema-internal references without additional configuration. Not supporting $ref for internal schema definitions makes it painful to write complex schemas.