**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
#
#
from datetime import timedelta
from unittest import mock
import pytest
from parameterized import parameterized
from airflow.api_connexion.exceptions import EXCEPTIONS_LINK_MAP
from airflow.models import DAG, DagModel, DagRun
from airflow.security import permissions
from airflow.utils import timezone
from airflow.utils.session import create_session, provide_session
from airflow.utils.types import DagRunType
from tests.test_utils.api_connexion_utils import assert_401, create_user, delete_user
from tests.test_utils.config import conf_vars
from tests.test_utils.db import clear_db_dags, clear_db_runs
@pytest.fixture(scope="module")
def configured_app(minimal_app_for_api):
    app = minimal_app_for_api
    create_user(
        app,  
        username="test",
        role_name="Test",
        permissions=[
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_EDIT, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_CREATE, permissions.RESOURCE_DAG_RUN),
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG_RUN),