Update lago.py to accomodate API change (BerriAI#5495) (BerriAI#5543)

* Update lago.py to accomodate API change (BerriAI#5495)

external_customer_id is deprecated. 

external_subscription_id is the replacement.

* fix(lago.py): fixes

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---------

Co-authored-by: Raymond Weitekamp <19483938+rawwerks@users.noreply.github.com>

docs/my-website/docs/proxy/billing.md

@@ -23,7 +23,7 @@ Bill internal teams for their usage
 Set 'lago' as a callback on your proxy config.yaml
 
 ```yaml
-model_name:
+model_list:
   - model_name: fake-openai-endpoint
     litellm_params:
       model: openai/fake

litellm/integrations/lago.py

@@ -114,7 +114,7 @@ def _common_logic(self, kwargs: dict, response_obj) -> dict:
         returned_val = {
             "event": {
                 "transaction_id": str(uuid.uuid4()),
-                "external_customer_id": external_customer_id,
+                "external_subscription_id": external_customer_id,
                 "code": os.getenv("LAGO_API_EVENT_CODE"),
                 "properties": {"model": model, "response_cost": cost, **usage},
             }
@@ -189,6 +189,8 @@ async def async_log_success_event(self, kwargs, response_obj, start_time, end_ti
             )
 
             response.raise_for_status()
+
+            verbose_logger.debug(f"Logged Lago Object: {response.text}")
         except Exception as e:
             if response is not None and hasattr(response, "text"):
                 litellm.print_verbose(f"\nError Message: {response.text}")