ShareLinks plugin: guest share links for Jellyfin

Includes fix for redemption failing with DbUpdateConcurrencyException:
change the guest password before applying the user policy, since
UpdatePolicyAsync bumps the user's EF concurrency token and a stale
instance then breaks ChangePassword.

Jellyfin.Plugin.ShareLinks/Plugin.cs

@@ -0,0 +1,46 @@
+using System;
+using System.Collections.Generic;
+using MediaBrowser.Common.Configuration;
+using MediaBrowser.Common.Plugins;
+using MediaBrowser.Model.Plugins;
+using MediaBrowser.Model.Serialization;
+using Jellyfin.Plugin.ShareLinks.Configuration;
+
+namespace Jellyfin.Plugin.ShareLinks;
+
+/// <summary>
+/// ShareLinks plugin. Creates expiring guest-share links for Jellyfin items
+/// without persisting raw tokens.
+/// </summary>
+public class Plugin : BasePlugin<PluginConfiguration>, IHasWebPages
+{
+    /// <summary>Initializes a new instance of the <see cref="Plugin"/> class.</summary>
+    public Plugin(IApplicationPaths applicationPaths, IXmlSerializer xmlSerializer)
+        : base(applicationPaths, xmlSerializer)
+    {
+        Instance = this;
+    }
+
+    /// <summary>Gets the current plugin instance.</summary>
+    public static Plugin? Instance { get; private set; }
+
+    /// <inheritdoc />
+    public override string Name => "ShareLinks";
+
+    /// <inheritdoc />
+    public override string Description =>
+        "Secure expiring share links for Jellyfin items with guest-user lockdown.";
+
+    /// <inheritdoc />
+    public override Guid Id => Guid.Parse("68540b76-ee74-436d-85ff-2abc884bbea6");
+
+    /// <inheritdoc />
+    public IEnumerable<PluginPageInfo> GetPages() => new[]
+    {
+        new PluginPageInfo
+        {
+            Name = "ShareLinks",
+            EmbeddedResourcePath = GetType().Namespace + ".Web.configPage.html"
+        }
+    };
+}