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/encoding.go

@@ -0,0 +1,43 @@
+// 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"
+)
+
+const (
+	EncodingLabel = "encoding"
+)
+
+type Encoding struct {
+	ContentType   low.NodeReference[string]
+	Headers       low.NodeReference[map[low.KeyReference[string]]low.ValueReference[*Header]]
+	Style         low.NodeReference[string]
+	Explode       low.NodeReference[bool]
+	AllowReserved low.NodeReference[bool]
+}
+
+func (en *Encoding) FindHeader(hType string) *low.ValueReference[*Header] {
+	return low.FindItemInMap[*Header](hType, en.Headers.Value)
+}
+
+func (en *Encoding) Build(root *yaml.Node, idx *index.SpecIndex) error {
+
+	headers, hL, hN, err := low.ExtractMapFlat[*Header](HeadersLabel, root, idx)
+	if err != nil {
+		return err
+	}
+	if headers != nil {
+		en.Headers = low.NodeReference[map[low.KeyReference[string]]low.ValueReference[*Header]]{
+			Value:     headers,
+			KeyNode:   hL,
+			ValueNode: hN,
+		}
+	}
+
+	return nil
+}