**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
"""Delete a DAG Run"""
    if session.query(DagRun).filter(DagRun.dag_id == dag_id, DagRun.run_id == dag_run_id).delete() == 0:
        raise NotFound(detail=f"DAGRun with DAG ID: '{dag_id}' and DagRun ID: '{dag_run_id}' not found")
    return NoContent, 204
@security.requires_access(
    [
        (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),
        (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG_RUN),
    ]
)
@provide_session
def get_dag_run(dag_id, dag_run_id, session):