Refactored version directory names

3.0 and 2.0 do not work, there are multiple versions and anything with a period in it sucks from my point of view, v2 and v3 feel much better from a DX perspective.

datamodel/low/v3/link.go

@@ -0,0 +1,41 @@
+// Copyright 2022 Princess B33f Heavy Industries / Dave Shanley
+// SPDX-License-Identifier: MIT
+
+package v3
+
+import (
+	"github.com/pb33f/libopenapi/datamodel/low"
+	"github.com/pb33f/libopenapi/index"
+	"gopkg.in/yaml.v3"
+)
+
+type Link struct {
+	OperationRef low.NodeReference[string]
+	OperationId  low.NodeReference[string]
+	Parameters   low.KeyReference[map[low.KeyReference[string]]low.ValueReference[string]]
+	RequestBody  low.NodeReference[string]
+	Description  low.NodeReference[string]
+	Server       low.NodeReference[*Server]
+	Extensions   map[low.KeyReference[string]]low.ValueReference[any]
+}
+
+func (l *Link) FindParameter(pName string) *low.ValueReference[string] {
+	return low.FindItemInMap[string](pName, l.Parameters.Value)
+}
+
+func (l *Link) FindExtension(ext string) *low.ValueReference[any] {
+	return low.FindItemInMap[any](ext, l.Extensions)
+}
+
+func (l *Link) Build(root *yaml.Node, idx *index.SpecIndex) error {
+	l.Extensions = low.ExtractExtensions(root)
+
+	// extract server.
+	ser, sErr := low.ExtractObject[*Server](ServerLabel, root, idx)
+	if sErr != nil {
+		return sErr
+	}
+	l.Server = ser
+
+	return nil
+}