update auth.py

backend/auth.py

@@ -1,2 +1,19 @@
 from database import execute
 import bcrypt
+
+def create_user(username, password):
+
+    password_hash = bcrypt.hashpw(
+        password.encode(),
+        bcrypt.gensalt()
+    ).decode()
+
+    user_id = execute(
+        """
+        INSERT INTO users (username, password_hash)
+        VALUES (?, ?)
+        """,
+        (username, password_hash)
+    )
+
+    return user_id