Starting implementation of helper functions to encrypt and decrypt Oauth tokens before storing them. Added requirement python-dotenv and cryptography

requirements.txt

@@ -2,4 +2,5 @@ fastapi
 uvicorn[standard]
 sqlalchemy
 httpx
-cryptography
+cryptography
+python-dotenv

security.py

@@ -0,0 +1,40 @@
+import os
+import json
+from cryptography.fernet import Fernet
+from dotenv import load_dotenv
+
+# Load environment variables from a .env file for local development
+load_dotenv()
+
+# It is CRITICAL that this key is set in your environment and kept secret.
+# It should be a 32-url-safe-base64-encoded key.
+ENCRYPTION_KEY = os.getenv("ENCRYPTION_KEY")
+
+if not ENCRYPTION_KEY:
+    raise ValueError("ENCRYPTION_KEY is not set in the environment. Please generate a key and add it to your .env file.")
+
+# Ensure the key is in bytes for the Fernet instance
+fernet = Fernet(ENCRYPTION_KEY.encode())
+
+def encrypt_tokens(access_token: str, refresh_token: str) -> str:
+    """
+    Combines access and refresh tokens into a JSON object, then encrypts it.
+    """
+    tokens = {"access_token": access_token, "refresh_token": refresh_token}
+    tokens_json_string = json.dumps(tokens)
+    encrypted_data = fernet.encrypt(tokens_json_string.encode())
+    return encrypted_data.decode()
+
+def decrypt_tokens(encrypted_data_str: str) -> dict:
+    """
+    Decrypts the token string back into a dictionary of tokens.
+    """
+    decrypted_data_bytes = fernet.decrypt(encrypted_data_str.encode())
+    tokens_json_string = decrypted_data_bytes.decode()
+    return json.loads(tokens_json_string)
+
+def generate_key():
+    """
+    Utility function to generate a new encryption key. Run this once.
+    """
+    return Fernet.generate_key().decode()