The XCom endpoint joins the XCom and DagRun tables. Currently, the output of the join isn't getting stored as a new `query` variable, as seen in the link to the following PR. We should add a new test to check that these tables are getting joined correctly.

https://github.com/apache/airflow/pull/10594/files/1fe1da978763c9919cee0d2c7eccd96438631993#diff-aa0c2f68c6177fb1587a6de6b5cfb28cR59


I will make these changes after #10594 
tests/api_connexion/endpoints/test_xcom_endpoint.py
'dag_id': dag_id_1,
                        'execution_date': execution_date,
                        'key': 'test-xcom-key-1',
                        'task_id': task_id_1,
                        'timestamp': "TIMESTAMP",
                    },
                    {
                        'dag_id': dag_id_1,
                        'execution_date': execution_date,
                        'key': 'test-xcom-key-2',
                        'task_id': task_id_1,
                        'timestamp': "TIMESTAMP",
                    },
                ],
                'total_entries': 2,
            },
        )
    def test_should_raises_401_unauthenticated(self):
        dag_id = 'test-dag-id'
        task_id = 'test-task-id'
        execution_date = '2005-04-02T00:00:00+00:00'
        execution_date_parsed = parse_execution_date(execution_date)
        dag_run_id = DR.generate_run_id(DagRunType.MANUAL, execution_date_parsed)
        self._create_xcom_entries(dag_id, dag_run_id, execution_date_parsed, task_id)
        response = self.client.get(
            f"/api/v1/dags/{dag_id}/dagRuns/{dag_run_id}/taskInstances/{task_id}/xcomEntries"
        )
        assert_401(response)
    @provide_session
    def _create_xcom_entries(self, dag_id, dag_run_id, execution_date, task_id, session=None):