catch openai rate limit error (#7658)

api/services/errors/llm.py

@@ -0,0 +1,19 @@
+from typing import Optional
+
+
+class InvokeError(Exception):
+    """Base class for all LLM exceptions."""
+
+    description: Optional[str] = None
+
+    def __init__(self, description: Optional[str] = None) -> None:
+        self.description = description
+
+    def __str__(self):
+        return self.description or self.__class__.__name__
+
+
+class InvokeRateLimitError(InvokeError):
+    """Raised when the Invoke returns rate limit error."""
+
+    description = "Rate Limit Error"