Nodes - Added node type registration system

Nodes - Moved models and node logic into core
Nodes - Added node service that leverages DI

src/Artemis.Core/Services/NodeService.cs

@@ -0,0 +1,79 @@
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using Ninject;
+
+namespace Artemis.Core.Services
+{
+    internal class NodeService : INodeService
+    {
+        private readonly IKernel _kernel;
+
+        #region Constants
+
+        private static readonly Type TYPE_NODE = typeof(INode);
+
+        #endregion
+
+        #region Properties & Fields
+
+        public IEnumerable<NodeData> AvailableNodes => NodeTypeStore.GetAll();
+
+        #endregion
+
+        #region Constructors
+
+        public NodeService(IKernel kernel)
+        {
+            _kernel = kernel;
+        }
+
+        #endregion
+
+        #region Methods
+
+        public NodeTypeRegistration RegisterNodeType(Plugin plugin, Type nodeType)
+        {
+            if (plugin == null) throw new ArgumentNullException(nameof(plugin));
+            if (nodeType == null) throw new ArgumentNullException(nameof(nodeType));
+
+            if (!TYPE_NODE.IsAssignableFrom(nodeType)) throw new ArgumentException("Node has to be a base type of the Node-Type.", nameof(nodeType));
+
+            NodeAttribute? nodeAttribute = nodeType.GetCustomAttribute<NodeAttribute>();
+            string name = nodeAttribute?.Name ?? nodeType.Name;
+            string description = nodeAttribute?.Description ?? string.Empty;
+            string category = nodeAttribute?.Category ?? string.Empty;
+
+            NodeData nodeData = new(plugin, nodeType, name, description, category, () => CreateNode(nodeType));
+            return NodeTypeStore.Add(nodeData);
+        }
+
+        private INode CreateNode(Type nodeType)
+        {
+            INode node = _kernel.Get(nodeType) as INode ?? throw new InvalidOperationException($"Node {nodeType} is not an INode");
+            if (node.CustomViewModelType != null)
+                node.CustomViewModel = _kernel.Get(node.CustomViewModelType);
+            return node;
+        }
+
+        #endregion
+    }
+
+    /// <summary>
+    /// A service that provides access to the node system
+    /// </summary>
+    public interface INodeService : IArtemisService
+    {
+        /// <summary>
+        /// Gets all available nodes
+        /// </summary>
+        IEnumerable<NodeData> AvailableNodes { get; }
+
+        /// <summary>
+        /// Initializes a node of the provided <paramref name="nodeType"/>
+        /// </summary>
+        /// <param name="plugin">The plugin the node belongs to</param>
+        /// <param name="nodeType">The type of node to initialize</param>
+        NodeTypeRegistration RegisterNodeType(Plugin plugin, Type nodeType);
+    }
+}