fix(models): resolve ambiguous foreign keys between User and InviteCode

test_error.py

@@ -0,0 +1,8 @@
+from app.main import app  
+from fastapi.testclient import TestClient  
+c = TestClient(app)  
+import sqlite3  
+conn = sqlite3.connect('data.db')  
+cur = conn.execute('SELECT id, username, invited_by_code_id FROM users')  
+print(cur.fetchall())  
+conn.close()