Added SQL, dao and app - not functional

dao.py

@@ -0,0 +1,8 @@
+from functions.database import execute_query
+
+def get_user_by_email(email):
+    query = "SELECT * FROM users WHERE email = %s"
+    cursor = execute_query(query, (email,))
+    if cursor:
+        return cursor.fetchone()
+    return None