feat: use SecretStr for inference provider auth credentials

- RemoteInferenceProviderConfig now has auth_credential: SecretStr
- the default alias is api_key (most common name)
- some providers override to use api_token (RunPod, vLLM, Databricks)
- some providers exclude it (Ollama, TGI, Vertex AI)

llama_stack/providers/remote/inference/sambanova/config.py

@@ -6,7 +6,7 @@
 
 from typing import Any
 
-from pydantic import BaseModel, Field, SecretStr
+from pydantic import BaseModel, Field
 
 from llama_stack.providers.utils.inference.model_registry import RemoteInferenceProviderConfig
 from llama_stack.schema_utils import json_schema_type
@@ -25,10 +25,6 @@ class SambaNovaImplConfig(RemoteInferenceProviderConfig):
         default="https://api.sambanova.ai/v1",
         description="The URL for the SambaNova AI server",
     )
-    api_key: SecretStr | None = Field(
-        default=None,
-        description="The SambaNova cloud API Key",
-    )
 
     @classmethod
     def sample_run_config(cls, api_key: str = "${env.SAMBANOVA_API_KEY:=}", **kwargs) -> dict[str, Any]:

llama_stack/providers/remote/inference/sambanova/sambanova.py

@@ -19,9 +19,6 @@ class SambaNovaInferenceAdapter(OpenAIMixin):
     SambaNova Inference Adapter for Llama Stack.
     """
 
-    def get_api_key(self) -> str:
-        return self.config.api_key.get_secret_value() if self.config.api_key else ""
-
     def get_base_url(self) -> str:
         """
         Get the base URL for OpenAI mixin.