Import december-2020-12-18 from private repo (scrubbed 2026-05-27)

Targets Rec Room 2020.12.18 client.

Re-import after adding:
- DorkNet.ClientMod/dorknet-clientmod.json.template — config schema
  the launcher's manifest-driven patcher renders into UserData/.
- tools/build-patcher-zip.ps1 — produces the dorknet-clientpatch-{key}.zip
  Release asset the launcher fetches.
- .github/workflows/release.yml — auto-publishes both Release assets
  on v1-december-* tag push.

Scrubbed via maintainer-side scrub-for-public.ps1: same drop rules as
the prior import, plus build-patcher-zip.ps1 added to the tools/
allow-list so it survives the scrub.

DorkNet.Server/Controllers/API/Notification/V2/NotificationController.cs

@@ -0,0 +1,34 @@
+using Microsoft.AspNetCore.Mvc;
+using DorkNet.Server.Services;
+
+namespace DorkNet.Server.Controllers.API.Notification.V2;
+
+/// <summary>
+/// Legacy raw-WebSocket notification endpoint. Replaced by the SignalR
+/// hub at <c>notify.{apex}/hub/v1</c>. Returns 410 Gone for any client
+/// that still tries the old path.
+/// </summary>
+[ApiController]
+[Route("api/[controller]/v2")]
+public class NotificationController(DomainConfig domain) : ControllerBase
+{
+    [HttpGet]
+    public IActionResult Connect() => StatusCode(StatusCodes.Status410Gone, new
+    {
+        error = "use_signalr_hub",
+        hint = $"connect to {domain.Sub("notify")}/hub/v1 instead",
+    });
+
+    /// <summary>GET <c>api/notification/hub/v1</c> — returns the
+    /// SignalR hub URL the client should open. Without this the
+    /// watch falls back to its own default and may try the wrong
+    /// scheme. URL is built off the configured deployment apex
+    /// (DORKNET_DOMAIN).</summary>
+    [HttpGet("/api/notification/hub/v1")]
+    public IActionResult HubInfo() => Ok(new
+    {
+        Url = $"https://{domain.Sub("notify")}/hub/v1",
+        Protocol = "signalr",
+        Version = 1,
+    });
+}