**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**


airflow/api_connexion/endpoints/dag_run_endpoint.py
"""Get a DAG Run."""
    dag_run = session.query(DagRun).filter(DagRun.dag_id == dag_id, DagRun.run_id == dag_run_id).one_or_none()
    if dag_run is None:
        raise NotFound(
            "DAGRun not found",
            detail=f"DAGRun with DAG ID: '{dag_id}' and DagRun ID: '{dag_run_id}' not found",
        )
    return dagrun_schema.dump(dag_run)
@security.requires_access(
    [
        (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),
        (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG_RUN),
    ]
)
@format_parameters(
    {
        'start_date_gte': format_datetime,
        'start_date_lte': format_datetime,
        'execution_date_gte': format_datetime,
        'execution_date_lte': format_datetime,
        'end_date_gte': format_datetime,
        'end_date_lte': format_datetime,
        'limit': check_limit,
    }
)
@provide_session
def get_dag_runs(