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_test.go

@@ -0,0 +1,80 @@
+// 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"
+	"github.com/stretchr/testify/assert"
+	"gopkg.in/yaml.v3"
+	"testing"
+)
+
+func TestLink_Build(t *testing.T) {
+
+	yml := `operationRef: '#/someref'
+operationId: someId
+parameters:
+  param1: something
+  param2: somethingElse
+requestBody: somebody
+description: this is a link object.
+server:
+  url: https://pb33f.io
+x-linky: slinky  
+`
+
+	var idxNode yaml.Node
+	_ = yaml.Unmarshal([]byte(yml), &idxNode)
+	idx := index.NewSpecIndex(&idxNode)
+
+	var n Link
+	err := low.BuildModel(&idxNode, &n)
+	assert.NoError(t, err)
+
+	err = n.Build(idxNode.Content[0], idx)
+	assert.NoError(t, err)
+
+	assert.Equal(t, "#/someref", n.OperationRef.Value)
+	assert.Equal(t, "someId", n.OperationId.Value)
+	assert.Equal(t, "this is a link object.", n.Description.Value)
+
+	ext := n.FindExtension("x-linky")
+	assert.NotNil(t, ext)
+	assert.Equal(t, "slinky", ext.Value)
+
+	param1 := n.FindParameter("param1")
+	assert.Equal(t, "something", param1.Value)
+	param2 := n.FindParameter("param2")
+	assert.Equal(t, "somethingElse", param2.Value)
+
+	assert.NotNil(t, n.Server.Value)
+	assert.Equal(t, "https://pb33f.io", n.Server.Value.URL.Value)
+
+}
+
+func TestLink_Build_Fail(t *testing.T) {
+
+	yml := `operationRef: '#/someref'
+operationId: someId
+parameters:
+  param1: something
+  param2: somethingElse
+requestBody: somebody
+description: this is a link object.
+server:
+  $ref: #bork`
+
+	var idxNode yaml.Node
+	_ = yaml.Unmarshal([]byte(yml), &idxNode)
+	idx := index.NewSpecIndex(&idxNode)
+
+	var n Link
+	err := low.BuildModel(&idxNode, &n)
+	assert.NoError(t, err)
+
+	err = n.Build(idxNode.Content[0], idx)
+	assert.Error(t, err)
+
+}