add rate limiting support in inbound call server

vocode/telephony/inbound_call_server.py

@@ -1,4 +1,5 @@
 from fastapi import FastAPI, Response, Form
+from typing import Optional
 import requests
 import uvicorn
 from .. import api_key, BASE_URL
@@ -8,25 +9,33 @@ from ..models.telephony import CreateInboundCall
 
 VOCODE_INBOUND_CALL_URL = f"https://{BASE_URL}/create_inbound_call"
 
-class InboundCallServer():
 
-    def __init__(self, agent_config: AgentConfig):
+class InboundCallServer:
+    def __init__(
+        self, agent_config: AgentConfig, response_on_rate_limit: Optional[str] = None
+    ):
         self.agent_config = agent_config
         self.app = FastAPI()
         self.app.post("/vocode")(self.handle_call)
+        self.response_on_rate_limit = (
+            response_on_rate_limit
+            or "The line is really busy right now, check back later!"
+        )
 
-    async def handle_call(self, twilio_sid: str = Form(alias='CallSid')):
+    async def handle_call(self, twilio_sid: str = Form(alias="CallSid")):
         response = requests.post(
             VOCODE_INBOUND_CALL_URL,
-            headers={
-                "Authorization": f"Bearer {api_key}"
-            },
+            headers={"Authorization": f"Bearer {api_key}"},
             json=CreateInboundCall(
-                agent_config=self.agent_config,
-                twilio_sid=twilio_sid
-            ).dict()
+                agent_config=self.agent_config, twilio_sid=twilio_sid
+            ).dict(),
         )
-        assert response.ok
+        if response.status_code == 429:
+            return Response(
+                f"<Response><Say>{self.response_on_rate_limit}</Say></Response>",
+                media_type="application/xml",
+            )
+        assert response.ok, response.text
         return Response(
             response.text,
             media_type="application/xml",