**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/schemas/dag_run_schema.py
"""List of DAGRuns with metadata"""
    dag_runs: List[DagRun]
    total_entries: int
class DAGRunCollectionSchema(Schema):
    """DAGRun Collection schema"""
    dag_runs = fields.List(fields.Nested(DAGRunSchema))
    total_entries = fields.Int()
class DagRunsBatchFormSchema(Schema):
    """Schema to validate and deserialize the Form(request payload) submitted to DagRun Batch endpoint"""
    class Meta:
        """Meta"""
        datetimeformat = 'iso'
        strict = True
    order_by = fields.String()
    page_offset = fields.Int(load_default=0, validate=Range(min=0))
    page_limit = fields.Int(load_default=100, validate=Range(min=1))
    dag_ids = fields.List(fields.Str(), load_default=None)
    execution_date_gte = fields.DateTime(load_default=None, validate=validate_istimezone)
    execution_date_lte = fields.DateTime(load_default=None, validate=validate_istimezone)
    start_date_gte = fields.DateTime(load_default=None, validate=validate_istimezone)
    start_date_lte = fields.DateTime(load_default=None, validate=validate_istimezone)
    end_date_gte = fields.DateTime(load_default=None, validate=validate_istimezone)
    end_date_lte = fields.DateTime(load_default=None, validate=validate_istimezone)
dagrun_schema = DAGRunSchema()
dagrun_collection_schema = DAGRunCollectionSchema()
dagruns_batch_form_schema = DagRunsBatchFormSchema()