feat: Bring Your Own API (BYOA) (#2228)

# What does this PR do?

Prototype on a new feature to allow new APIs to be plugged in Llama
Stack. Opened for early feedback on the approach and test appetite on
the functionality.

@ashwinb @raghotham open for early feedback, thanks!

---------

Signed-off-by: Sébastien Han <seb@redhat.com>
Co-authored-by: Ashwin Bharambe <ashwin.bharambe@gmail.com>

tests/external/llama-stack-api-weather/src/llama_stack_api_weather/__init__.py

@@ -0,0 +1,11 @@
+# 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.
+
+"""Weather API for Llama Stack."""
+
+from .weather import WeatherProvider, available_providers
+
+__all__ = ["WeatherProvider", "available_providers"]

tests/external/llama-stack-api-weather/src/llama_stack_api_weather/weather.py

@@ -0,0 +1,39 @@
+# 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.
+
+from typing import Protocol
+
+from llama_stack.providers.datatypes import AdapterSpec, Api, ProviderSpec, RemoteProviderSpec
+from llama_stack.schema_utils import webmethod
+
+
+def available_providers() -> list[ProviderSpec]:
+    return [
+        RemoteProviderSpec(
+            api=Api.weather,
+            provider_type="remote::kaze",
+            config_class="llama_stack_provider_kaze.KazeProviderConfig",
+            adapter=AdapterSpec(
+                adapter_type="kaze",
+                module="llama_stack_provider_kaze",
+                pip_packages=["llama_stack_provider_kaze"],
+                config_class="llama_stack_provider_kaze.KazeProviderConfig",
+            ),
+        ),
+    ]
+
+
+class WeatherProvider(Protocol):
+    """
+    A protocol for the Weather API.
+    """
+
+    @webmethod(route="/weather/locations", method="GET")
+    async def get_available_locations() -> dict[str, list[str]]:
+        """
+        Get the available locations.
+        """
+        ...