[API Updates] Model / shield / memory-bank routing + agent persistence + support for private headers (#92)

This is yet another of those large PRs (hopefully we will have less and less of them as things mature fast). This one introduces substantial improvements and some simplifications to the stack.

Most important bits:

* Agents reference implementation now has support for session / turn persistence. The default implementation uses sqlite but there's also support for using Redis.

* We have re-architected the structure of the Stack APIs to allow for more flexible routing. The motivating use cases are:
  - routing model A to ollama and model B to a remote provider like Together
  - routing shield A to local impl while shield B to a remote provider like Bedrock
  - routing a vector memory bank to Weaviate while routing a keyvalue memory bank to Redis

* Support for provider specific parameters to be passed from the clients. A client can pass data using `x_llamastack_provider_data` parameter which can be type-checked and provided to the Adapter implementations.

llama_stack/apis/models/client.py

@@ -0,0 +1,71 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+import asyncio
+
+from typing import List, Optional
+
+import fire
+import httpx
+from termcolor import cprint
+
+from .models import *  # noqa: F403
+
+
+class ModelsClient(Models):
+    def __init__(self, base_url: str):
+        self.base_url = base_url
+
+    async def initialize(self) -> None:
+        pass
+
+    async def shutdown(self) -> None:
+        pass
+
+    async def list_models(self) -> List[ModelServingSpec]:
+        async with httpx.AsyncClient() as client:
+            response = await client.get(
+                f"{self.base_url}/models/list",
+                headers={"Content-Type": "application/json"},
+            )
+            response.raise_for_status()
+            return [ModelServingSpec(**x) for x in response.json()]
+
+    async def get_model(self, core_model_id: str) -> Optional[ModelServingSpec]:
+        async with httpx.AsyncClient() as client:
+            response = await client.get(
+                f"{self.base_url}/models/get",
+                params={
+                    "core_model_id": core_model_id,
+                },
+                headers={"Content-Type": "application/json"},
+            )
+            response.raise_for_status()
+            j = response.json()
+            if j is None:
+                return None
+            return ModelServingSpec(**j)
+
+
+async def run_main(host: str, port: int, stream: bool):
+    client = ModelsClient(f"http://{host}:{port}")
+
+    response = await client.list_models()
+    cprint(f"list_models response={response}", "green")
+
+    response = await client.get_model("Meta-Llama3.1-8B-Instruct")
+    cprint(f"get_model response={response}", "blue")
+
+    response = await client.get_model("Llama-Guard-3-8B")
+    cprint(f"get_model response={response}", "red")
+
+
+def main(host: str, port: int, stream: bool = True):
+    asyncio.run(run_main(host, port, stream))
+
+
+if __name__ == "__main__":
+    fire.Fire(main)

llama_stack/apis/models/models.py

@@ -4,11 +4,29 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
-from typing import Protocol
+from typing import List, Optional, Protocol
 
-from llama_models.schema_utils import webmethod  # noqa: F401
+from llama_models.llama3.api.datatypes import Model
 
-from pydantic import BaseModel  # noqa: F401
+from llama_models.schema_utils import json_schema_type, webmethod
+from pydantic import BaseModel, Field
+
+from llama_stack.distribution.datatypes import GenericProviderConfig
 
 
-class Models(Protocol): ...
+@json_schema_type
+class ModelServingSpec(BaseModel):
+    llama_model: Model = Field(
+        description="All metadatas associated with llama model (defined in llama_models.models.sku_list).",
+    )
+    provider_config: GenericProviderConfig = Field(
+        description="Provider config for the model, including provider_id, and corresponding config. ",
+    )
+
+
+class Models(Protocol):
+    @webmethod(route="/models/list", method="GET")
+    async def list_models(self) -> List[ModelServingSpec]: ...
+
+    @webmethod(route="/models/get", method="GET")
+    async def get_model(self, core_model_id: str) -> Optional[ModelServingSpec]: ...