Update models for event sourcing

tests/models/test_user.py

@@ -0,0 +1,23 @@
+import pytest
+from sqlalchemy.exc import IntegrityError
+from sqlalchemy.orm import Session
+
+from dibbler.models import User
+
+
+def insert_test_data(sql_session: Session) -> User:
+    user = User("Test User")
+    sql_session.add(user)
+    sql_session.commit()
+
+    return user
+
+
+def test_ensure_no_duplicate_user_names(sql_session: Session):
+    user = insert_test_data(sql_session)
+
+    user2 = User(user.name)
+    sql_session.add(user2)
+
+    with pytest.raises(IntegrityError):
+        sql_session.commit()