refactor ClassDiagramGenerator

Author: akravtsova

src/PlantUmlClassDiagramGenerator.Library/ClassDiagramGenerator/AdditionalTypeGenerator.cs

@@ -0,0 +1,35 @@
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+
+namespace PlantUmlClassDiagramGenerator.Library.ClassDiagramGenerator;
+
+public partial class ClassDiagramGenerator
+{
+    private void GenerateAdditionalTypeDeclarations()
+    {
+        for (int i = 0; i < additionalTypeDeclarationNodes.Count; i++)
+        {
+            SyntaxNode node = additionalTypeDeclarationNodes[i];
+            if (node is GenericNameSyntax genericNode)
+            {
+                if (createAssociation)
+                {
+                    GenerateAdditionalGenericTypeDeclaration(genericNode);
+                }
+                continue;
+            }
+            Visit(node);
+        }
+    }
+
+    private void GenerateAdditionalGenericTypeDeclaration(GenericNameSyntax genericNode)
+    {
+        var typename = TypeNameText.From(genericNode);
+        if (!types.Contains(typename.Identifier))
+        {
+            WriteLine($"class {typename.Identifier}{typename.TypeArguments} {{");
+            WriteLine("}");
+            types.Add(typename.Identifier);
+        }
+    }
+}