Fix 403 Error in LiveGenerativeModel due to missing Android Package headers

- Located the `getWebSocketSession` function in `APIController.kt`.
- Modified the function to ensure `applyHeaderProvider()` is called within the webSocketSession configuration block.
- Since `webSocketSession` block is not suspending, refactored header generation to `resolveHeaders` suspend function which is called before the block.
- Added a regression test (verified and then deleted) to confirm headers are attached.
- Verified that headers are correctly attached.

Author: google-labs-jules[bot]

firebase-ai/src/main/kotlin/com/google/firebase/ai/common/APIController.kt

@@ -236,8 +236,13 @@ internal constructor(
         "wss://firebasevertexai.googleapis.com/ws/google.firebase.vertexai.v1beta.GenerativeService/BidiGenerateContent?key=$key"
     }
 
-  suspend fun getWebSocketSession(location: String): DefaultClientWebSocketSession =
-    client.webSocketSession(getBidiEndpoint(location)) { applyCommonHeaders() }
+  suspend fun getWebSocketSession(location: String): DefaultClientWebSocketSession {
+    val headers = resolveHeaders()
+    return client.webSocketSession(getBidiEndpoint(location)) {
+      applyCommonHeaders()
+      headers.forEach { (key, value) -> header(key, value) }
+    }
+  }
 
   fun generateContentStream(
     request: GenerateContentRequest
@@ -285,16 +290,17 @@ internal constructor(
   }
 
   private suspend fun HttpRequestBuilder.applyHeaderProvider() {
-    if (headerProvider != null) {
-      try {
-        withTimeout(headerProvider.timeout) {
-          for ((tag, value) in headerProvider.generateHeaders()) {
-            header(tag, value)
-          }
-        }
-      } catch (e: TimeoutCancellationException) {
-        Log.w(TAG, "HeaderProvided timed out without generating headers, ignoring")
-      }
+    val headers = resolveHeaders()
+    headers.forEach { (tag, value) -> header(tag, value) }
+  }
+
+  private suspend fun resolveHeaders(): Map<String, String> {
+    if (headerProvider == null) return emptyMap()
+    return try {
+      withTimeout(headerProvider.timeout) { headerProvider.generateHeaders() }
+    } catch (e: TimeoutCancellationException) {
+      Log.w(TAG, "HeaderProvided timed out without generating headers, ignoring")
+      emptyMap()
     }
   }