Add GraphView module & the World Storage inspector window into the main branch

All final changes into the main branch

Assets/ETSI.ARF/ARF World Storage API/Editor/Graph/ARFEdgeLink.cs

+//
+// ARF - Augmented Reality Framework (ETSI ISG ARF)
+//
+// Copyright 2022 ETSI
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Last change: July 2022
+//
+
+using Assets.ETSI.ARF.ARF_World_Storage_API.Editor.Windows;
+using Org.OpenAPITools.Model;
+using UnityEditor;
+using UnityEditor.Experimental.GraphView;
+using UnityEngine;
+using UnityEngine.UIElements;
+
+namespace Assets.ETSI.ARF.ARF_World_Storage_API.Editor.Graph
+{
+    public class ARFEdgeLink : Edge
+    {
+        public WorldLink worldLink;
+        public string GUID;
+
+        public Image savedIcon;
+
+        public ARFEdgeLink()
+        {
+            var doubleClickManipulator = new Clickable(Clicked);
+            doubleClickManipulator.activators.Clear();
+            doubleClickManipulator.activators.Add(new ManipulatorActivationFilter { button = MouseButton.LeftMouse, clickCount = 2 });
+            this.AddManipulator(doubleClickManipulator);
+        }
+        public void Clicked()
+        {
+            Debug.Log(worldLink.ToJson());
+            GraphEditorWindow.ShowWindow(this);
+        }
+        public void MarkUnsaved()
+        {
+            if (savedIcon == null)
+            {
+                //the icon to add if the node does not correspond to an element in the server
+                Texture2D warningImage = (Texture2D)AssetDatabase.LoadAssetAtPath("Assets/ETSI.ARF/ARF World Storage API/Images/cloud.png", typeof(Texture2D));
+                savedIcon = new Image
+                {
+                    image = warningImage
+                };
+                savedIcon.style.width = 18;
+                savedIcon.style.height = 18;
+                savedIcon.style.minWidth = 18;
+                savedIcon.style.minHeight = 18;
+                savedIcon.style.flexGrow = 1;
+                savedIcon.style.alignSelf = Align.Center;
+
+            }
+            if (!edgeControl.Contains(savedIcon))
+            {
+                edgeControl.Add(savedIcon);
+            }
+            tooltip = "This element is not synchronized with the World Storage";
+        }
+
+        public void MarkSaved()
+        {
+            if (edgeControl.Contains(savedIcon))
+            {
+                edgeControl.Remove(savedIcon);
+                tooltip = "";
+            }
+        }
+    }
+}
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