Support checking provider /models endpoints on proxy /v1/models endpoint (#9958)

* feat(utils.py): support global flag for 'check_provider_endpoints'

enables setting this for `/models` on proxy

* feat(utils.py): add caching to 'get_valid_models'

Prevents checking endpoint repeatedly

* fix(utils.py): ensure mutations don't impact cached results

* test(test_utils.py): add unit test to confirm cache invalidation logic

* feat(utils.py): get_valid_models - support passing litellm params dynamically

Allows for checking endpoints based on received credentials

* test: update test

* feat(model_checks.py): pass router credentials to get_valid_models - ensures it checks correct credentials

* refactor(utils.py): refactor for simpler functions

* fix: fix linting errors

* fix(utils.py): fix test

* fix(utils.py): set valid providers to custom_llm_provider, if given

* test: update test

* fix: fix ruff check error

litellm/proxy/proxy_server.py

@@ -803,9 +803,9 @@ model_max_budget_limiter = _PROXY_VirtualKeyModelMaxBudgetLimiter(
     dual_cache=user_api_key_cache
 )
 litellm.logging_callback_manager.add_litellm_callback(model_max_budget_limiter)
-redis_usage_cache: Optional[RedisCache] = (
-    None  # redis cache used for tracking spend, tpm/rpm limits
-)
+redis_usage_cache: Optional[
+    RedisCache
+] = None  # redis cache used for tracking spend, tpm/rpm limits
 user_custom_auth = None
 user_custom_key_generate = None
 user_custom_sso = None
@@ -1131,9 +1131,9 @@ async def update_cache(  # noqa: PLR0915
         _id = "team_id:{}".format(team_id)
         try:
             # Fetch the existing cost for the given user
-            existing_spend_obj: Optional[LiteLLM_TeamTable] = (
-                await user_api_key_cache.async_get_cache(key=_id)
-            )
+            existing_spend_obj: Optional[
+                LiteLLM_TeamTable
+            ] = await user_api_key_cache.async_get_cache(key=_id)
             if existing_spend_obj is None:
                 # do nothing if team not in api key cache
                 return
@@ -2812,9 +2812,9 @@ async def initialize(  # noqa: PLR0915
         user_api_base = api_base
         dynamic_config[user_model]["api_base"] = api_base
     if api_version:
-        os.environ["AZURE_API_VERSION"] = (
-            api_version  # set this for azure - litellm can read this from the env
-        )
+        os.environ[
+            "AZURE_API_VERSION"
+        ] = api_version  # set this for azure - litellm can read this from the env
     if max_tokens:  # model-specific param
         dynamic_config[user_model]["max_tokens"] = max_tokens
     if temperature:  # model-specific param
@@ -3316,6 +3316,7 @@ async def model_list(
         user_model=user_model,
         infer_model_from_keys=general_settings.get("infer_model_from_keys", False),
         return_wildcard_routes=return_wildcard_routes,
+        llm_router=llm_router,
     )
 
     return dict(
@@ -7758,9 +7759,9 @@ async def get_config_list(
                             hasattr(sub_field_info, "description")
                             and sub_field_info.description is not None
                         ):
-                            nested_fields[idx].field_description = (
-                                sub_field_info.description
-                            )
+                            nested_fields[
+                                idx
+                            ].field_description = sub_field_info.description
                         idx += 1
 
                     _stored_in_db = None