Reintroduced FromList method as [Obsolete]

This was removed from `ReadOnlyKeyedTopicCollection<T>` since the use case is better covered by the similar constructor overload, but should have been kept with an obsolete notice to provide instructions to callers.

In addition, the `ReadOnlyKeyedTopicCollection<T>` used to be named `ReadOnlyTopicCollection<T>`, from which a `ReadOnlyTopicCollection` was derived. The `ReadOnlyTopicCollection` no longer derives from `ReadOnlyKeyedTopicCollection<T>`. But since callers may confuse it with the previous class of the same name—which was based on a `KeyedCollection`—I've introduced it there as well, in order to offer instruction to implementors.

Author: JeremyCaney

OnTopic/Collections/ReadOnlyKeyedTopicCollection{T}.cs

@@ -35,6 +35,19 @@ public class ReadOnlyKeyedTopicCollection<T> : ReadOnlyCollection<T> where T : T
       _innerCollection = innerCollection as KeyedTopicCollection<T>?? new(innerCollection);
     }
 
+    /*==========================================================================================================================
+    | FACTORY METHOD: FROM LIST
+    \-------------------------------------------------------------------------------------------------------------------------*/
+    /// <summary>
+    ///   Establishes a new <see cref="ReadOnlyTopicCollection{T}"/> based on an existing <see cref="List{T}"/>.
+    /// </summary>
+    /// <remarks>
+    ///   The <paramref name="innerCollection"/> will be converted to a <see cref="TopicCollection{T}"/>.
+    /// </remarks>
+    /// <param name="innerCollection">The underlying <see cref="TopicCollection{T}"/>.</param>
+    [Obsolete("This is effectively satisfied by the related overload, and has been removed.", true)]
+    public ReadOnlyTopicCollection<T> FromList(IList<T> innerCollection) => throw new NotImplementedException();
+
     /*==========================================================================================================================
     | METHOD: GET VALUE
     \-------------------------------------------------------------------------------------------------------------------------*/

OnTopic/Collections/ReadOnlyTopicCollection.cs

@@ -27,6 +27,19 @@ public class ReadOnlyTopicCollection : ReadOnlyCollection<Topic> {
     public ReadOnlyTopicCollection(IList<Topic>? innerCollection = null) : base(innerCollection?? new List<Topic>()) {
     }
 
+    /*==========================================================================================================================
+    | FACTORY METHOD: FROM LIST
+    \-------------------------------------------------------------------------------------------------------------------------*/
+    /// <summary>
+    ///   Establishes a new <see cref="ReadOnlyTopicCollection"/> based on an existing <see cref="List{Topic}"/>.
+    /// </summary>
+    /// <remarks>
+    ///   The <paramref name="innerCollection"/> will be converted to a <see cref="ReadOnlyTopicCollection"/>.
+    /// </remarks>
+    /// <param name="innerCollection">The underlying <see cref="List{Topic}"/>.</param>
+    [Obsolete("This is effectively satisfied by the related overload, and has been removed.", true)]
+    public ReadOnlyTopicCollection FromList(IList<Topic> innerCollection) => throw new NotImplementedException();
+
     /*==========================================================================================================================
     | METHOD: GET TOPIC
     \-------------------------------------------------------------------------------------------------------------------------*/