feat: add s3 provider to files API

Signed-off-by: Sébastien Han <seb@redhat.com>

llama_stack/providers/remote/files/object/s3/persistence.py

@@ -0,0 +1,76 @@
+# 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 json
+import logging
+from datetime import datetime, timezone
+
+from pydantic import BaseModel
+
+from llama_stack.apis.files.files import FileUploadResponse
+from llama_stack.providers.utils.kvstore import KVStore
+
+log = logging.getLogger(__name__)
+
+
+class UploadSessionInfo(BaseModel):
+    """Information about an upload session."""
+
+    upload_id: str
+    bucket: str
+    key: str
+    mime_type: str
+    size: int
+    url: str
+    created_at: datetime
+
+
+class S3FilesPersistence:
+    def __init__(self, kvstore: KVStore):
+        self._kvstore = kvstore
+        self._store = None
+
+    async def _get_store(self) -> KVStore:
+        """Get the kvstore instance, initializing it if needed."""
+        if self._store is None:
+            self._store = await anext(self._kvstore)
+        return self._store
+
+    async def store_upload_session(
+        self, session_info: FileUploadResponse, bucket: str, key: str, mime_type: str, size: int
+    ):
+        """Store upload session information."""
+        upload_info = UploadSessionInfo(
+            upload_id=session_info.id,
+            bucket=bucket,
+            key=key,
+            mime_type=mime_type,
+            size=size,
+            url=session_info.url,
+            created_at=datetime.now(timezone.utc),
+        )
+
+        store = await self._get_store()
+        await store.set(
+            key=f"upload_session:{session_info.id}",
+            value=upload_info.model_dump_json(),
+        )
+
+    async def get_upload_session(self, upload_id: str) -> UploadSessionInfo | None:
+        """Get upload session information."""
+        store = await self._get_store()
+        value = await store.get(
+            key=f"upload_session:{upload_id}",
+        )
+        if not value:
+            return None
+
+        return UploadSessionInfo(**json.loads(value))
+
+    async def delete_upload_session(self, upload_id: str) -> None:
+        """Delete upload session information."""
+        store = await self._get_store()
+        await store.delete(key=f"upload_session:{upload_id}")