(feat): Added Reference tracking to low-level model #25

When building a document, everything that IS NOT a schema is auto-resolved in the model, this is very convenient because it creates a nice tree to explore and there is no need to perform lookups to when using `$ref` instead of inline definitions.

The issue is however being able to determine if the node was originally a reference or not, that data was lost, including the name of the reference used. This use case surfaced in issue #25, where the need to know what is and what is not referenced has different requirements for different applications.

This update now tracks that data and makes it available in `NodeReference` and `ValueReference` for every property.

Signed-off-by: Dave Shanley <dave@quobix.com>

datamodel/low/v3/callback.go

@@ -48,7 +48,7 @@ func (cb *Callback) Build(root *yaml.Node, idx *index.SpecIndex) error {
 			currentCB = callbackNode
 			continue
 		}
-		callback, eErr := low.ExtractObjectRaw[*PathItem](callbackNode, idx)
+		callback, eErr, isRef, rv := low.ExtractObjectRaw[*PathItem](callbackNode, idx)
 		if eErr != nil {
 			return eErr
 		}
@@ -56,8 +56,10 @@ func (cb *Callback) Build(root *yaml.Node, idx *index.SpecIndex) error {
 			Value:   currentCB.Value,
 			KeyNode: currentCB,
 		}] = low.ValueReference[*PathItem]{
-			Value:     callback,
-			ValueNode: callbackNode,
+			Value:       callback,
+			ValueNode:   callbackNode,
+			IsReference: isRef,
+			Reference:   rv,
 		}
 	}
 	if len(callbacks) > 0 {