U4-8530 Make it possbile to hide preview button by DocumentType or ContentItem

src/Umbraco.Web.UI.Client/src/views/content/edit.html

@@ -58,7 +58,7 @@
                </umb-button>
 
                <umb-button
-                  ng-if="!page.isNew && content.preview"
+                  ng-if="!page.isNew && content.allowPreview"
                   type="button"
                   action="preview(content)"
                   label="Preview page"

src/Umbraco.Web/Models/ContentEditing/ContentItemDisplay.cs

@@ -22,7 +22,7 @@ namespace Umbraco.Web.Models.ContentEditing
     {
         public ContentItemDisplay()
         {
-            Preview = true;
+            AllowPreview = true;
         }
 
         [DataMember(Name = "publishDate")]
@@ -40,8 +40,14 @@ namespace Umbraco.Web.Models.ContentEditing
         [DataMember(Name = "urls")]
         public string[] Urls { get; set; }
 
-        [DataMember( Name = "preview" )]
-        public bool Preview { get; set; }
+        /// <summary>
+        /// Determines whether previewing is allowed for this node
+        /// </summary>
+        /// <remarks>
+        /// By default this is true but by using events developers can toggle this off for certain documents if there is nothing to preview
+        /// </remarks>
+        [DataMember( Name = "allowPreview" )]
+        public bool AllowPreview { get; set; }
 
         /// <summary>
         /// The allowed 'actions' based on the user's permissions - Create, Update, Publish, Send to publish

src/Umbraco.Web/Models/Mapping/ContentModelMapper.cs

@@ -66,6 +66,7 @@ namespace Umbraco.Web.Models.Mapping
                             ? new[] {"Cannot generate urls without a current Umbraco Context"}
                             : content.GetContentUrls(UmbracoContext.Current)))
                 .ForMember(display => display.Properties, expression => expression.Ignore())
+                .ForMember(display => display.AllowPreview, expression => expression.Ignore())
                 .ForMember(display => display.TreeNodeUrl, expression => expression.Ignore())
                 .ForMember(display => display.Notifications, expression => expression.Ignore())
                 .ForMember(display => display.Errors, expression => expression.Ignore())