Merge branch 'feature/IncomingRelationshipAttribute' into develop

Offers support for adding an `IncomingRelationshipAttribute` content type and corresponding attribute view component to the OnTopic Editor. This commit does not provide that implementation, it simply permits the editor to offer that implementation without needing to extend the `DefaultTopicLookupService`.

Author: JeremyCaney

OnTopic/DefaultTopicLookupService.cs

@@ -45,6 +45,7 @@ public DefaultTopicLookupService(IEnumerable<Type>? types = null, Type? defaultT
       TryAdd(typeof(FileListAttribute));
       TryAdd(typeof(FilePathAttribute));
       TryAdd(typeof(HtmlAttribute));
+      TryAdd(typeof(IncomingRelationshipAttribute));
       TryAdd(typeof(InstructionAttribute));
       TryAdd(typeof(LastModifiedAttribute));
       TryAdd(typeof(LastModifiedByAttribute));

OnTopic/Metadata/AttributeDescriptor.cs

@@ -56,8 +56,8 @@ public abstract class AttributeDescriptor : Topic {
     /// </remarks>
     /// <param name="key">A string representing the key for the new topic instance.</param>
     /// <param name="contentType">A string representing the key of the target content type.</param>
-    /// <param name="id">The unique identifier assigned by the data store for an existing topic.</param>
     /// <param name="parent">Optional topic to set as the new topic's parent.</param>
+    /// <param name="id">The unique identifier assigned by the data store for an existing topic.</param>
     /// <exception cref="ArgumentException">
     ///   Thrown when the class representing the content type is found, but doesn't derive from <see cref="Topic"/>.
     /// </exception>

OnTopic/Metadata/AttributeTypes/IncomingRelationshipAttribute.cs

@@ -0,0 +1,40 @@
+/*==============================================================================================================================
+| Author        Ignia, LLC
+| Client        Ignia, LLC
+| Project       Topics Library
+\=============================================================================================================================*/
+
+namespace OnTopic.Metadata.AttributeTypes {
+
+  /*============================================================================================================================
+  | CLASS: INCOMING RELATIONSHIP ATTRIBUTE (DESCRIPTOR)
+  \---------------------------------------------------------------------------------------------------------------------------*/
+  /// <summary>
+  ///   Represents metadata for describing an incoming relationship attribute type, including information on how it will be
+  ///   presented and validated in the editor.
+  /// </summary>
+  /// <remarks>
+  ///   This class is primarily used by the Topic Editor interface to determine how attributes are displayed as part of the
+  ///   CMS; except in very specific scenarios, it is not typically used elsewhere in the Topic Library itself.
+  /// </remarks>
+  public class IncomingRelationshipAttribute : AttributeTypeDescriptor {
+
+    /*==========================================================================================================================
+    | CONSTRUCTOR
+    \-------------------------------------------------------------------------------------------------------------------------*/
+    /// <inheritdoc />
+    public IncomingRelationshipAttribute(
+      string key,
+      string contentType,
+      Topic parent,
+      int id = -1
+    ) : base(
+      key,
+      contentType,
+      parent,
+      id
+    ) {
+    }
+
+  } //Class
+} //Namespace