feat(templates): add TemplateFolder entity and Template.FolderId

tests/ScadaLink.Commons.Tests/Entities/TemplateFolderTests.cs

@@ -0,0 +1,30 @@
+using ScadaLink.Commons.Entities.Templates;
+using Xunit;
+
+namespace ScadaLink.Commons.Tests.Entities;
+
+public class TemplateFolderTests
+{
+    [Fact]
+    public void Constructor_SetsName()
+    {
+        var folder = new TemplateFolder("Dev");
+
+        Assert.Equal("Dev", folder.Name);
+        Assert.Null(folder.ParentFolderId);
+        Assert.Equal(0, folder.SortOrder);
+    }
+
+    [Fact]
+    public void Constructor_NullName_Throws()
+    {
+        Assert.Throws<ArgumentNullException>(() => new TemplateFolder(null!));
+    }
+
+    [Fact]
+    public void Template_FolderId_DefaultsToNull()
+    {
+        var template = new Template("X");
+        Assert.Null(template.FolderId);
+    }
+}