Converted *Url fields to use the Uri type

This takes advantage of functionality introduced as part of #6d74fbf, which allows mapping of `Uri` types. It also allows more flexibility in views, as we can now parse parts of the URL if we prefer or need.

Author: JeremyCaney

OnTopic.ViewModels/ContentItemTopicViewModel.cs

@@ -4,6 +4,8 @@
 | Project       Topics Library
 \=============================================================================================================================*/
 
+using System;
+
 namespace OnTopic.ViewModels {
 
   /*============================================================================================================================
@@ -33,15 +35,15 @@ public class ContentItemTopicViewModel: ItemTopicViewModel {
     /// <summary>
     ///   Gets an optional URL for additional information that should be linked to.
     /// </summary>
-    public string? LearnMoreUrl { get; set; }
+    public Uri? LearnMoreUrl { get; set; }
 
     /*==========================================================================================================================
     | THUMBNAIL IMAGE
     \-------------------------------------------------------------------------------------------------------------------------*/
     /// <summary>
     ///   Gets an optional path to a thumbnail image that should accompany the content item.
     /// </summary>
-    public string? ThumbnailImage { get; set; }
+    public Uri? ThumbnailImage { get; set; }
 
     /*==========================================================================================================================
     | CATEGORY

OnTopic.ViewModels/SectionTopicViewModel.cs

@@ -4,6 +4,8 @@
 | Project       Topics Library
 \=============================================================================================================================*/
 
+using System;
+
 namespace OnTopic.ViewModels {
 
   /*============================================================================================================================
@@ -25,7 +27,7 @@ public class SectionTopicViewModel : TopicViewModel {
     /// <summary>
     ///   Provides a header image which may be displayed at the top of a section.
     /// </summary>
-    public string? HeaderImageUrl { get; set; }
+    public Uri? HeaderImageUrl { get; set; }
 
   } //Class
 } //Namespace

OnTopic.ViewModels/VideoTopicViewModel.cs

@@ -4,6 +4,8 @@
 | Project       Topics Library
 \=============================================================================================================================*/
 
+using System;
+
 namespace OnTopic.ViewModels {
 
   /*============================================================================================================================
@@ -25,15 +27,15 @@ public class VideoTopicViewModel: PageTopicViewModel {
     /// <summary>
     ///   Provides a URL reference to a video to display on the page.
     /// </summary>
-    public string? VideoUrl { get; set; }
+    public Uri? VideoUrl { get; set; }
 
     /*==========================================================================================================================
     | POSTER URL
     \-------------------------------------------------------------------------------------------------------------------------*/
     /// <summary>
     ///   Provides a URL reference to an image to display prior to playing the video.
     /// </summary>
-    public string? PosterUrl { get; set; }
+    public Uri? PosterUrl { get; set; }
 
   } //Class
 } //Namespace