Improve display of job result and properties

It's quite common that job properties and/or result are strings. Since everything is serialized as JSON in the database, a string becomes quoted and has escaped characters. For displaying in the dashboard, it's nicer without the quotes and escaped characters.

src/Hangfire.Core/Common/StringExtensions.cs

@@ -0,0 +1,29 @@
+using System;
+
+namespace Hangfire.Common
+{
+    internal static class StringExtensions
+    {
+        /// <summary>
+        /// Returns the deserialized JSON <paramref name="text"/> if the text is a serialized JSON string,
+        /// or the specified text without any transformation if the text is not a serialized JSON string.
+        /// </summary>
+        /// <param name="text">The text to prettify.</param>
+        public static string PrettyJsonString(this string text)
+        {
+            if (text.StartsWith("\"", StringComparison.Ordinal))
+            {
+                try
+                {
+                    return SerializationHelper.Deserialize<string>(text, SerializationOption.User);
+                }
+                catch
+                {
+                    // Ignore
+                }
+            }
+
+            return text;
+        }
+    }
+}

src/Hangfire.Core/Dashboard/JobHistoryRenderer.cs

@@ -195,8 +195,8 @@ public static NonEscapedString SucceededRenderer(HtmlHelper html, IDictionary<st
 
             if (stateData.TryGetValue("Result", out var resultString) && !String.IsNullOrWhiteSpace(resultString))
             {
-                var result = stateData["Result"];
-                builder.Append($"<dt>Result:</dt><dd>{html.HtmlEncode(result)}</dd>");
+                var result = stateData["Result"].PrettyJsonString();
+                builder.Append($"<dt>Result:</dt><dd>{html.HtmlEncode(result).Replace("\n", "<br>")}</dd>");
 
                 itemsAdded = true;
             }

src/Hangfire.Core/Dashboard/Pages/JobDetailsPage.cshtml

@@ -118,7 +118,7 @@
                     {
                         <tr>
                             <td class="width-20 word-break">@parameter.Key</td>
-                            <td><pre><code>@parameter.Value</code></pre></td>
+                            <td><pre><code>@parameter.Value.PrettyJsonString()</code></pre></td>
                         </tr>
                     }
                 </table>

src/Hangfire.Core/Dashboard/Pages/JobDetailsPage.cshtml.cs

@@ -473,7 +473,7 @@ public override void Execute()
 
 
             #line 121 "..\..\Dashboard\Pages\JobDetailsPage.cshtml"
-                                      Write(parameter.Value);
+                                      Write(parameter.Value.PrettyJsonString());
 
 
             #line default