**Description**

It would be great having a option to abort a DAG Runs through the REST API.

**Use case / motivation**

The proposed input params would be:
 - DAG_ID
 - DAG_RUN_ID

The DAG Run should abort all its tasks running and mark them as "failed".

**Are you willing to submit a PR?**

**Related Issues**


tests/api_connexion/endpoints/test_dag_run_endpoint.py
def test_should_respond_200(self):
        self._create_test_dag_run()
        response = self.client.post(
            "api/v1/dags/~/dagRuns/list",
            json={"dag_ids": ["TEST_DAG_ID"]},
            environ_overrides={'REMOTE_USER': "test"},
        )
        assert response.status_code == 200
        assert response.json == {
            "dag_runs": [
                {
                    'dag_id': 'TEST_DAG_ID',
                    'dag_run_id': 'TEST_DAG_RUN_ID_1',
                    'end_date': None,
                    'state': 'running',
                    'execution_date': self.default_time,
                    'logical_date': self.default_time,
                    'external_trigger': True,
                    'start_date': self.default_time,
                    'conf': {},
                },