Marked Description property as [Obsolete]

The `Topic` class contains a number of convenience methods for accessing (and setting) popular attributes. These were useful back when we worked directly with the `Topic` entities in our views (ugh!). Since we now use view models (e.g., `ITopicViewModel`) alongside the `TopicMappingService`, these don't provide as much benefit, as we can expose strongly typed accessor properties on our view models as needed, and have them automatically mapped to attributes. Given this, we're removing accessor properties that don't include business logic and aren't widely used within our libraries.

I also updated the `ReverseTopicMappingServiceTest` to account for this change, as it used the accessor method in one of its unit tests.

There are other convenience methods we will be keeping for now because they provide internal benefits. For instance, `IsHidden` and `IsDisabled` are frequently used by the library itself. Also, `Title` has the benefit of providing a fallback to `Key` if the `Title` isn't provided, which is useful—and especially since this accessor is utilized by the `TopicMappingService`.

Author: JeremyCaney

OnTopic.Tests/ReverseTopicMappingServiceTest.cs

@@ -140,7 +140,8 @@ public async Task Map_Existing_ReturnsUpdatedTopic() {
       target.DefaultValue       = "Hello";
       target.IsRequired         = true;
       target.IsExtendedAttribute= false;
-      target.Description        = "Original Description";
+
+      target.Attributes.SetValue("Description", "Original Description");
 
       target                    = (TextAttribute?)await mappingService.MapAsync(bindingModel, target).ConfigureAwait(false);
 
@@ -150,7 +151,7 @@ public async Task Map_Existing_ReturnsUpdatedTopic() {
       Assert.AreEqual<string>("World", target.DefaultValue);
       Assert.AreEqual<bool>(false, target.IsRequired);
       Assert.AreEqual<bool>(false, target.IsExtendedAttribute);
-      Assert.AreEqual<string>("Original Description", target.Description);
+      Assert.AreEqual<string>("Original Description", target.Attributes.GetValue("Description"));
 
     }
 

OnTopic/Topic.cs

@@ -368,6 +368,7 @@ public string Title {
     /// <requires description="The value from the getter must be provided." exception="T:System.ArgumentNullException">
     ///   !string.IsNullOrWhiteSpace(value)
     /// </requires>
+    [Obsolete("The Description convenience property will be removed in OnTopic Library 5.0. Use Attributes.SetValue() instead.")]
     public string? Description {
       get => Attributes.GetValue("Description");
       set => SetAttributeValue("Description", value);