JSON-LD Context Generator: Generate "@type": "@id" when appropriate.

[timothee-haudebourg]

In a JSON-LD context term definition, the binding "@type": "@id" is used to specify that any string literal as value of this term should be interpreted as a node identifier. For TreeLDR, this is when the layout of a field can be a reference.

For instance:

type Foo {
	bar: &rdfs:Resource
}

This should generate the following LD context:

{
	"bar": {
		"@id": "https://example.org/bar",
		"@type": "@id"
	}
}

This should also work with a union layout where one of the term is a reference:

type Foo {
	bar: &rdfs:Resource | rdfs:Resource
}