fix: avoid duplicate using statements (#57)

This PR eliminates duplicate using statements in generated C# code by consolidating namespace declarations and filtering out duplicates.

### Key changes:
- Filters out "System" namespace from dynamic using statements to avoid duplication with hardcoded System import
- Consolidates hardcoded Mockerade namespace imports with dynamic namespace arrays
- Applies deduplication and sorting to all using statement generation

Author: vbreuss

Source/Mockerade.SourceGenerators/Internals/SourceGeneration.ExtensionsClass.cs

@@ -10,18 +10,15 @@ internal static partial class SourceGeneration
 {
 	public static string GetExtensionClass(string name, Class @class)
 	{
-		string[] namespaces = @class.GetClassNamespaces();
+		string[] namespaces = [.. @class.GetClassNamespaces(), "Mockerade.Checks", "Mockerade.Events", "Mockerade.Setup"];
 		StringBuilder sb = new();
 		sb.AppendLine(Header);
-		foreach (string @namespace in namespaces)
+		foreach (string @namespace in namespaces.Distinct().OrderBy(n => n))
 		{
 			sb.Append("using ").Append(@namespace).AppendLine(";");
 		}
 
 		sb.Append("""
-		          using Mockerade.Checks;
-		          using Mockerade.Events;
-		          using Mockerade.Setup;
 
 		          namespace Mockerade;
 		          

Source/Mockerade.SourceGenerators/Internals/SourceGeneration.MockClass.cs

@@ -10,18 +10,15 @@ internal static partial class SourceGeneration
 {
 	public static string GetMockClass(string name, MockClass mockClass)
 	{
-		string[] namespaces = mockClass.GetAllNamespaces();
+		string[] namespaces = [.. mockClass.GetAllNamespaces(), "Mockerade.Checks", "Mockerade.Events", "Mockerade.Setup"];
 		StringBuilder sb = new();
 		sb.AppendLine(Header);
-		foreach (string @namespace in namespaces)
+		foreach (string @namespace in namespaces.Distinct().OrderBy(n => n))
 		{
 			sb.Append("using ").Append(@namespace).AppendLine(";");
 		}
 
 		sb.Append("""
-		          using Mockerade.Checks;
-		          using Mockerade.Events;
-		          using Mockerade.Setup;
 
 		          namespace Mockerade;
 

Source/Mockerade.SourceGenerators/Internals/SourceGeneration.RegisterMocks.cs

@@ -10,7 +10,7 @@ public static string RegisterMocks(ICollection<(string Name, MockClass MockClass
 		var sb = new StringBuilder();
 		sb.AppendLine(Header);
 		sb.AppendLine("using System;");
-		foreach (string? @namespace in mocks.Select(x => x.MockClass.Namespace).Distinct().OrderBy(x => x))
+		foreach (string? @namespace in mocks.Select(x => x.MockClass.Namespace).Where(x => x != "System").Distinct().OrderBy(x => x))
 		{
 			sb.Append("using ").Append(@namespace).AppendLine(";");
 		}