feat: add s3 provider to files API

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

tests/unit/providers/files/test_remote_files_s3.py

@@ -0,0 +1,35 @@
+import pytest
+
+from llama_stack.providers.remote.files.object.s3.config import S3FilesImplConfig
+from llama_stack.providers.remote.files.object.s3.s3_files import S3FilesAdapter
+
+
+@pytest.fixture
+def s3_config():
+    return S3FilesImplConfig(
+        aws_access_key_id="test-key",
+        aws_secret_access_key="test-secret",
+        region_name="us-east-1",
+        endpoint_url="http://localhost:9000",
+    )
+
+
+@pytest.fixture
+async def s3_files(s3_config):
+    adapter = S3FilesAdapter(s3_config)
+    await adapter.initialize()
+    return adapter
+
+
+@pytest.mark.asyncio
+async def test_create_upload_session(s3_files):
+    bucket = "test-bucket"
+    key = "test-file.txt"
+    mime_type = "text/plain"
+    size = 1024
+
+    response = await s3_files.create_upload_session(bucket, key, mime_type, size)
+    assert response.id == f"{bucket}/{key}"
+    assert response.size == size
+    assert response.offset == 0
+    assert response.url is not None