Added InstructionAttribute

This is in preparation of introducing a new attribute type—`IncomingRelationshipAttribute`—to the editor. In the future, we'd prefer for these to be managed via the editor itself, but for now this interdependency remains.

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/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