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/Models/ShareLinkStatus.cs

@@ -0,0 +1,13 @@
+namespace Jellyfin.Plugin.ShareLinks.Models;
+
+/// <summary>Lifecycle state of a share link.</summary>
+public enum ShareLinkStatus
+{
+    Pending = 0,
+    Active = 1,
+    Redeemed = 2,
+    Expired = 3,
+    Revoked = 4,
+    Failed = 5,
+    Redeeming = 6
+}