feat: add support for global location in Vertex AI base URL

- Update _get_base_url method to handle 'global' location case
- Use 'aiplatform.googleapis.com' for global locations
- Use '{location}-aiplatform.googleapis.com' for regional locations
- Maintains backward compatibility with existing regional endpoints

src/pipecat/services/google/llm_vertex.py

@@ -83,14 +83,23 @@ class GoogleVertexLLMService(OpenAILLMService):
         self._api_key = self._get_api_token(credentials, credentials_path)
 
         super().__init__(
-            api_key=self._api_key, base_url=base_url, model=model, params=params, **kwargs
+            api_key=self._api_key,
+            base_url=base_url,
+            model=model,
+            params=params,
+            **kwargs,
         )
 
     @staticmethod
     def _get_base_url(params: InputParams) -> str:
         """Construct the base URL for Vertex AI API."""
+        # Determine the correct API host based on location
+        if params.location == "global":
+            api_host = "aiplatform.googleapis.com"
+        else:
+            api_host = f"{params.location}-aiplatform.googleapis.com"
         return (
-            f"https://{params.location}-aiplatform.googleapis.com/v1/"
+            f"https://{api_host}/v1/"
             f"projects/{params.project_id}/locations/{params.location}/endpoints/openapi"
         )
 
@@ -118,12 +127,14 @@ class GoogleVertexLLMService(OpenAILLMService):
         if credentials:
             # Parse and load credentials from JSON string
             creds = service_account.Credentials.from_service_account_info(
-                json.loads(credentials), scopes=["https://www.googleapis.com/auth/cloud-platform"]
+                json.loads(credentials),
+                scopes=["https://www.googleapis.com/auth/cloud-platform"],
             )
         elif credentials_path:
             # Load credentials from JSON file
             creds = service_account.Credentials.from_service_account_file(
-                credentials_path, scopes=["https://www.googleapis.com/auth/cloud-platform"]
+                credentials_path,
+                scopes=["https://www.googleapis.com/auth/cloud-platform"],
             )
         else:
             try: