[LlamaStack][Fireworks] Update client and add unittest (#390)

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

@@ -4,6 +4,8 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
+from typing import Optional
+
 from llama_models.schema_utils import json_schema_type
 from pydantic import BaseModel, Field
 
@@ -14,7 +16,7 @@ class FireworksImplConfig(BaseModel):
         default="https://api.fireworks.ai/inference",
         description="The URL for the Fireworks server",
     )
-    api_key: str = Field(
-        default="",
+    api_key: Optional[str] = Field(
+        default=None,
         description="The Fireworks.ai API Key",
     )