feat: add club membership contract signing and city services

src/FrontOffice.BFF.WebApi/Hubs/TokenRelayHub.cs

@@ -0,0 +1,51 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.SignalR;
+using Microsoft.Extensions.Logging;
+
+namespace FrontOffice.BFF.WebApi.Hubs;
+
+/// <summary>
+/// SignalR Hub for relaying token notifications from CMS to Frontend clients.
+/// This hub is used by Frontend to receive token revocation/refresh notifications.
+/// </summary>
+[Authorize(Roles = "user")]
+public class TokenRelayHub : Hub
+{
+    private readonly ILogger<TokenRelayHub> _logger;
+
+    public TokenRelayHub(ILogger<TokenRelayHub> logger)
+    {
+        _logger = logger;
+    }
+
+    public override async Task OnConnectedAsync()
+    {
+        var userId = Context.User?.FindFirst("userId")?.Value;
+        if (!string.IsNullOrEmpty(userId))
+        {
+            // Subscribe this connection to the user's group for notifications
+            await Groups.AddToGroupAsync(Context.ConnectionId, $"user_{userId}");
+            _logger.LogInformation("Frontend client connected to TokenRelayHub: {ConnectionId}, UserId: {UserId}", 
+                Context.ConnectionId, userId);
+        }
+        else
+        {
+            _logger.LogWarning("Frontend client connected without userId: {ConnectionId}", Context.ConnectionId);
+        }
+        
+        await base.OnConnectedAsync();
+    }
+
+    public override async Task OnDisconnectedAsync(Exception? exception)
+    {
+        var userId = Context.User?.FindFirst("userId")?.Value;
+        if (!string.IsNullOrEmpty(userId))
+        {
+            await Groups.RemoveFromGroupAsync(Context.ConnectionId, $"user_{userId}");
+        }
+        
+        _logger.LogInformation("Frontend client disconnected from TokenRelayHub: {ConnectionId}, Exception: {Exception}", 
+            Context.ConnectionId, exception?.Message);
+        await base.OnDisconnectedAsync(exception);
+    }
+}