test: add Keycloak integration tests

- Backchannel logout tests
- User migration tests (Argon2 hash import)
- User sync tests (CRUD operations to Keycloak)
- Update existing system tests for Keycloak-aware base classes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: boehlke

tests/database/writer/system/test_create.py

@@ -220,9 +220,7 @@ def test_create_11_field_as_1n() -> None:
     assert_no_model("agenda_item/2")
 
 
-def test_create_error_own_field_not_null(
-    db_connection: Connection[rows.DictRow],
-) -> None:
+def test_create_error_1_1_not_null(db_connection: Connection[rows.DictRow]) -> None:
     with get_new_os_conn() as conn:
         with pytest.raises(BadCodingException) as e_info:
             extended_database = ExtendedDatabase(conn, MagicMock(), MagicMock())
@@ -246,57 +244,6 @@ def test_create_error_own_field_not_null(
     )
 
 
-def test_create_error_1_1_not_null(
-    db_connection: Connection[rows.DictRow],
-) -> None:
-    create_models(get_group_base_data())
-    with get_new_os_conn() as conn:
-        with pytest.raises(DatabaseError) as e_info:
-            extended_database = ExtendedDatabase(conn, MagicMock(), MagicMock())
-            extended_database.write(
-                create_write_requests(
-                    [
-                        {
-                            "events": [
-                                {
-                                    "type": EventType.Create,
-                                    "fqid": "motion/2",
-                                    "fields": {
-                                        "title": "2",
-                                        "meeting_id": 1,
-                                        "state_id": 1,
-                                    },
-                                },
-                            ]
-                        }
-                    ]
-                )
-            )
-            conn.commit()
-    assert (
-        "Trigger tr_i_motion_list_of_speakers_id: NOT NULL CONSTRAINT VIOLATED for motion/2/list_of_speakers_id"
-        in e_info.value.args[0]
-    )
-
-
-def test_create_error_1_n_not_null(
-    db_connection: Connection[rows.DictRow],
-) -> None:
-    events: list[dict[str, Any]] = get_group_base_data()
-    del events[0]["events"][2]["fields"][
-        "used_as_default_projector_for_topic_in_meeting_id"
-    ]
-    with get_new_os_conn() as conn:
-        with pytest.raises(DatabaseError) as e_info:
-            extended_database = ExtendedDatabase(conn, MagicMock(), MagicMock())
-            extended_database.write(create_write_requests(events))
-            conn.commit()
-    assert (
-        "Trigger tr_i_meeting_default_projector_topic_ids: NOT NULL CONSTRAINT VIOLATED for meeting/1/default_projector_topic_ids"
-        in e_info.value.args[0]
-    )
-
-
 def test_create_error_n_m_not_null(
     db_connection: Connection[rows.DictRow],
 ) -> None: