**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/endpoints/test_task_instance_endpoint.py
"priority_weight": 6,
            "queue": "default_queue",
            "queued_when": None,
            "sla_miss": {
                "dag_id": "example_python_operator",
                "description": None,
                "email_sent": False,
                "execution_date": "2020-01-01T00:00:00+00:00",
                "notification_sent": False,
                "task_id": "print_the_context",
                "timestamp": "2020-01-01T00:00:00+00:00",
            },
            "start_date": "2020-01-02T00:00:00+00:00",
            "state": "running",
            "task_id": "print_the_context",
            "try_number": 0,
            "unixname": getpass.getuser(),
        }
    def test_should_raises_401_unauthenticated(self):
        response = self.client.get(
            "api/v1/dags/example_python_operator/dagRuns/TEST_DAG_RUN_ID/taskInstances/print_the_context",
        )
        assert_401(response)
    def test_should_raise_403_forbidden(self):
        response = self.client.get(
            "api/v1/dags/example_python_operator/dagRuns/TEST_DAG_RUN_ID/taskInstances/print_the_context",
            environ_overrides={'REMOTE_USER': "test_no_permissions"},
        )
        assert response.status_code == 403
class TestGetTaskInstances(TestTaskInstanceEndpoint):