Generate Websocket token from auth in Unity WebGL build (#2988)

# Description of Changes

This is a fix for community bug which auth token is not used to create
Websocket connection in Unity WebGL build.
The issue here:
clockworklabs/com.clockworklabs.spacetimedbsdk#352

# API and ABI breaking changes

None

# Expected complexity level and risk

1

# Testing

- [ ] Using OAuth2.0 tokens, you should get the same `Identity` even
when the token is refreshed in the WebGL build

Author: FME849

src/Plugins/WebSocket.jslib

@@ -18,12 +18,33 @@ mergeInto(LibraryManager.library, {
         manager.callbacks.error = errorCallback;
     },
 
-    WebSocket_Connect: function(uriPtr, protocolPtr, authTokenPtr) {
+    WebSocket_Connect: async function(baseUriPtr, uriPtr, protocolPtr, authTokenPtr, callbackPtr) {
         try {
             var manager = this._webSocketManager;
+            var host = UTF8ToString(baseUriPtr);
             var uri = UTF8ToString(uriPtr);
             var protocol = UTF8ToString(protocolPtr);
             var authToken = UTF8ToString(authTokenPtr);
+            if (authToken)
+            {
+                var tokenUrl = new URL('v1/identity/websocket-token', host);
+                tokenUrl.protocol = host.startsWith("wss://") ? 'https:' : 'http:';
+                var headers = new Headers();
+                headers.set('Authorization', `Bearer ${authToken}`);
+
+                var response = await fetch(tokenUrl, {
+                    method: 'POST',
+                    headers: headers
+                });
+                if (response.ok) {
+                    const { token } = await response.json();
+                    if (token) {
+                        uri += `&token=${token}`;
+                    }
+                } else {
+                    throw new Error(`Failed to verify token: ${response.statusText}`);
+                }
+            }
 
             var socket = new window.WebSocket(uri, protocol);
             socket.binaryType = "arraybuffer";
@@ -63,10 +84,10 @@ mergeInto(LibraryManager.library, {
                 }
             };
 
-            return socketId;
+            dynCall('vi', callbackPtr, [socketId]);
         } catch (e) {
             console.error("WebSocket connection error:", e);
-            return -1;
+            dynCall('vi', callbackPtr, [-1]);
         }
     },
 

src/WebSocket.cs

@@ -75,7 +75,7 @@ IntPtr errorCallback
     );
 
     [DllImport("__Internal")]
-    private static extern int WebSocket_Connect(string uri, string protocol, string authToken);
+    private static extern int WebSocket_Connect(string host, string uri, string protocol, string authToken, IntPtr callbackPtr);
 
     [DllImport("__Internal")]
     private static extern int WebSocket_Send(int socketId, byte[] data, int length);
@@ -118,8 +118,15 @@ private static void WebGLOnError(int socketId)
         Instance?.HandleWebGLError(socketId);
     }
 
+    [AOT.MonoPInvokeCallback(typeof(Action<int>))]
+    private static void OnSocketIdReceived(int socketId)
+    {
+        Instance?._socketId.TrySetResult(socketId);
+    }
+
     private static WebSocket Instance;
     private int _webglSocketId = -1;
+    private TaskCompletionSource<int> _socketId;
 
     private void InitializeWebGL()
     {
@@ -145,7 +152,10 @@ public async Task Connect(string? auth, string host, string nameOrAddress, Conne
                 var uri = $"{host}/v1/database/{nameOrAddress}/subscribe?connection_id={connectionId}&compression={compression}";
                 if (light) uri += "&light=true";
 
-                _webglSocketId = WebSocket_Connect(uri, _options.Protocol, auth);
+                _socketId = new TaskCompletionSource<int>();
+                var callbackPtr = Marshal.GetFunctionPointerForDelegate((Action<int>)OnSocketIdReceived);
+                WebSocket_Connect(host, uri, _options.Protocol, auth, callbackPtr);
+                _webglSocketId = await _socketId.Task;
                 if (_webglSocketId == -1)
                 {
                     dispatchQueue.Enqueue(() => OnConnectError?.Invoke(