feat(commons): add DataType.List + ElementDataType companion for multi-value attributes

src/ZB.MOM.WW.ScadaBridge.Commons/Entities/Instances/InstanceAttributeOverride.cs

@@ -1,3 +1,5 @@
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
+
 namespace ZB.MOM.WW.ScadaBridge.Commons.Entities.Instances;
 
 public class InstanceAttributeOverride
@@ -10,6 +12,13 @@ public class InstanceAttributeOverride
     public string AttributeName { get; set; }
     /// <summary>Gets or sets the override value, or <c>null</c> to clear a previous override.</summary>
     public string? OverrideValue { get; set; }
+    /// <summary>
+    /// For <see cref="DataType.List"/> attributes: the scalar type of each
+    /// element (String, Int32, Float, Double, Boolean, DateTime). Null for scalar
+    /// attributes. The element type is fixed by the base attribute and cannot be
+    /// changed on a derived template or instance override.
+    /// </summary>
+    public DataType? ElementDataType { get; set; }
 
     /// <summary>Initializes a new <see cref="InstanceAttributeOverride"/> for the given attribute name.</summary>
     /// <param name="attributeName">The name of the attribute to override.</param>

src/ZB.MOM.WW.ScadaBridge.Commons/Entities/Templates/TemplateAttribute.cs

@@ -25,6 +25,13 @@ public class TemplateAttribute
     /// </summary>
     public DataType DataType { get; set; }
     /// <summary>
+    /// For <see cref="Enums.DataType.List"/> attributes: the scalar type of each
+    /// element (String, Int32, Float, Double, Boolean, DateTime). Null for scalar
+    /// attributes. The element type is fixed by the base attribute and cannot be
+    /// changed on a derived template or instance override.
+    /// </summary>
+    public DataType? ElementDataType { get; set; }
+    /// <summary>
     /// Gets or sets a value indicating whether the attribute is locked from override.
     /// </summary>
     public bool IsLocked { get; set; }

src/ZB.MOM.WW.ScadaBridge.Commons/Types/Enums/DataType.cs

@@ -8,5 +8,6 @@ public enum DataType
     Double,
     String,
     DateTime,
-    Binary
+    Binary,
+    List
 }

src/ZB.MOM.WW.ScadaBridge.Commons/Types/Flattening/FlattenedConfiguration.cs

@@ -66,6 +66,8 @@ public sealed record ResolvedAttribute
     public string? Value { get; init; }
     /// <summary>Gets the data type name.</summary>
     public string DataType { get; init; } = string.Empty;
+    /// <summary>For List attributes: the element scalar type name; null otherwise.</summary>
+    public string? ElementDataType { get; init; }
     /// <summary>Gets whether the attribute is locked.</summary>
     public bool IsLocked { get; init; }
     /// <summary>Gets the attribute description.</summary>