Support checking provider-specific /models endpoints for available models based on key (#7538)

* test(test_utils.py): initial test for valid models

Addresses https://github.com/BerriAI/litellm/issues/7525

* fix: test

* feat(fireworks_ai/transformation.py): support retrieving valid models from fireworks ai endpoint

* refactor(fireworks_ai/): support checking model info on `/v1/models` route

* docs(set_keys.md): update docs to clarify check llm provider api usage

* fix(watsonx/common_utils.py): support 'WATSONX_ZENAPIKEY' for iam auth

* fix(watsonx): read in watsonx token from env var

* fix: fix linting errors

* fix(utils.py): fix provider config check

* style: cleanup unused imports

litellm/llms/litellm_proxy/chat/transformation.py

@@ -0,0 +1,29 @@
+"""
+Translate from OpenAI's `/v1/chat/completions` to VLLM's `/v1/chat/completions`
+"""
+
+from typing import List, Optional, Tuple
+
+from litellm.secret_managers.main import get_secret_str
+
+from ...openai.chat.gpt_transformation import OpenAIGPTConfig
+
+
+class LiteLLMProxyChatConfig(OpenAIGPTConfig):
+    def _get_openai_compatible_provider_info(
+        self, api_base: Optional[str], api_key: Optional[str]
+    ) -> Tuple[Optional[str], Optional[str]]:
+        api_base = api_base or get_secret_str("LITELLM_PROXY_API_BASE")  # type: ignore
+        dynamic_api_key = api_key or get_secret_str("LITELLM_PROXY_API_KEY")
+        return api_base, dynamic_api_key
+
+    def get_models(
+        self, api_key: Optional[str] = None, api_base: Optional[str] = None
+    ) -> List[str]:
+        api_base, api_key = self._get_openai_compatible_provider_info(api_base, api_key)
+        if api_base is None:
+            raise ValueError(
+                "api_base not set for LiteLLM Proxy route. Set in env via `LITELLM_PROXY_API_BASE`"
+            )
+        models = super().get_models(api_key=api_key, api_base=api_base)
+        return [f"litellm_proxy/{model}" for model in models]