Add storage utilities and tests for file handling and tokens

Introduced new fixtures and tests for storage functionality, including saving files, generating URLs, and token creation/verification. Refactored `get_storage_provider` into a separate dependency module. Enhanced test coverage for improved reliability.

backend/tests/core/storage.py

@@ -0,0 +1,75 @@
+import os
+from io import BytesIO
+
+import pytest
+from fastapi import UploadFile
+
+from app.core.storage import LocalStorageProvider
+
+
+@pytest.fixture
+def test_storage():
+    """Create a test storage provider that uses a temp directory."""
+    import tempfile
+    test_dir = tempfile.mkdtemp()
+    provider = LocalStorageProvider(upload_folder=test_dir, files_url_path="/test-files")
+    yield provider
+    # Clean up
+    import shutil
+    shutil.rmtree(test_dir)
+
+
+@pytest.mark.asyncio  # Add this marker to run async tests
+async def test_save_file(test_storage):
+    """Test saving a file to storage."""
+    # Create a test file
+    content = b"test file content"
+    test_file = BytesIO(content)
+
+    # Create UploadFile with the correct parameters
+    file = UploadFile(
+        filename="test.txt",
+        file=test_file,
+    )
+    # Set content_type after creation
+    # file.content_type = "text/plain"
+
+    # Save the file
+    relative_path = "test-folder/test.txt"
+    saved_path = await test_storage.save_file(file, relative_path)
+
+    # Verify the file exists
+    full_path = os.path.join(test_storage.upload_folder, relative_path)
+    assert os.path.exists(full_path)
+
+    # Check the content
+    with open(full_path, "rb") as f:
+        saved_content = f.read()
+    assert saved_content == content
+
+    # Check the returned path
+    assert saved_path == relative_path
+
+
+def test_generate_presigned_url(test_storage):
+    """Test generating a presigned URL."""
+    file_path = "images/test.jpg"
+    filename = "test.jpg"
+    content_type = "image/jpeg"
+
+    upload_url, file_url = test_storage.generate_presigned_url(
+        file_path, filename, content_type
+    )
+
+    # Check the URLs
+    assert upload_url.startswith("/api/v1/uploads/")
+    assert file_url == f"/test-files/{file_path}"
+
+
+def test_get_file_url(test_storage):
+    """Test getting a file URL."""
+    file_path = "images/test.jpg"
+
+    url = test_storage.get_file_url(file_path)
+
+    assert url == f"/test-files/{file_path}"