Changed section data model

- Made parents nullable
- Added a data key for the tree
- Added depth for quicker layer-wise loading

I18N Commander/DataModel/Database/Common/DataContext.cs

@@ -35,6 +35,8 @@ public sealed class DataContext : DbContext
 
         modelBuilder.Entity<Section>().HasIndex(n => n.Id);
         modelBuilder.Entity<Section>().HasIndex(n => n.Name);
+        modelBuilder.Entity<Section>().HasIndex(n => n.Depth);
+        modelBuilder.Entity<Section>().HasIndex(n => n.DataKey);
 
         #endregion
 

I18N Commander/DataModel/Database/Section.cs

@@ -9,7 +9,11 @@ public sealed class Section
 
     public string Name { get; set; } = string.Empty;
 
-    public Section Parent { get; set; }
+    public string DataKey { get; set; } = string.Empty;
 
-    public List<TextElement> TextElements { get; set; }
+    public int Depth { get; set; } = 0;
+    
+    public Section? Parent { get; set; }
+
+    public List<TextElement> TextElements { get; set; } = new();
 }