JSON Schema recursive types

[Gallaecio]

Support recursive type definition (e.g. an item class has a field of its same type) by implementing $refs support, and use $refs as well when a given type is used more than once in the schema.

For example, given:

@dataclass
class Node:
    parent: Node | None
    children: list[Node] | None

Be able to get a JSON Schema like:

{
    "$defs": {
        "Node": {
            "type": "object",
            "properties": {
                "parent": {
                    "anyOf": [
                        {"type": "null"},
                        {"$ref": "#/$defs/Node"}
                    ]
                },
                "children": {
                    "anyOf": [
                        {"type": "null"},
                        {
                            "type": "array",
                            "items": {"$ref": "#/$defs/Node"},
                        }
                    ]
                }
            }
        },
    },
    "$ref": "#/$defs/Node"
}