**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
self.create_task_instances(session)
        session.query()
        sla_miss = SlaMiss(
            task_id="print_the_context",
            dag_id="example_python_operator",
            execution_date=self.default_time,
            timestamp=self.default_time,
        )
        session.add(sla_miss)
        session.commit()
        response = self.client.get(
            "/api/v1/dags/example_python_operator/dagRuns/TEST_DAG_RUN_ID/taskInstances/print_the_context",
            environ_overrides={"REMOTE_USER": "test"},
        )
        assert response.status_code == 200
        assert response.json == {
            "dag_id": "example_python_operator",
            "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": "PythonOperator",
            "pid": 100,
            "pool": "default_pool",
            "pool_slots": 1,