**Description**

I have noticed that the stable REST API doesn't have the ability to run a task (which is possible from the airflow web interface.
I think it would be nice to have either:
- Run task 
- Run all failing tasks (rerun from point of failure)
this ability for integrations.

**Use case / motivation**

I would like the ability to identify the failing tasks on a specific DAG Run and rerun only them.
I would like to do it remotely (non-interactive) using the REST API.
I could write a script that run only the failing tasks, but I couldn't find a way to "Run" a task, when I have the task instance ID.

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

Not at this stage

**Related Issues**



tests/api_connexion/schemas/test_task_instance_schema.py
"duration": 10000.0,
            "end_date": "2020-01-03T00:00:00+00:00",
            "execution_date": "2020-01-01T00:00:00+00:00",
            "executor_config": "{}",
            "hostname": "",
            "max_tries": 0,
            "operator": "DummyOperator",
            "pid": 100,
            "pool": "default_pool",
            "pool_slots": 1,
            "priority_weight": 1,
            "queue": "default_queue",
            "queued_when": None,
            "sla_miss": {
                "dag_id": "TEST_DAG_ID",
                "description": None,
                "email_sent": False,
                "execution_date": "2020-01-01T00:00:00+00:00",
                "notification_sent": False,
                "task_id": "TEST_TASK_ID",
                "timestamp": None,
            },
            "start_date": "2020-01-02T00:00:00+00:00",
            "state": "running",
            "task_id": "TEST_TASK_ID",
            "try_number": 0,
            "unixname": getpass.getuser(),
        }
        assert serialized_ti == expected_json
class TestClearTaskInstanceFormSchema(unittest.TestCase):