**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**



airflow/models/dag.py
if task_end_dates and next_run_date:
            min_task_end_date = min(task_end_dates)
            if next_run_date > min_task_end_date:
                return None
        return next_run_date
    def get_run_dates(self, start_date, end_date=None):
        """
        Returns a list of dates between the interval received as parameter using this
        dag's schedule interval. Returned dates can be used for execution dates.
        :param start_date: the start date of the interval
        :type start_date: datetime
        :param end_date: the end date of the interval, defaults to timezone.utcnow()
        :type end_date: datetime
        :return: a list of dates within the interval following the dag's schedule
        :rtype: list
        """
        run_dates = []
        using_start_date = start_date
        using_end_date = end_date
        
        using_start_date = using_start_date or min([t.start_date for t in self.tasks])
        using_end_date = using_end_date or timezone.utcnow()
        
        
        next_run_date = self.normalize_schedule(using_start_date) if not self.is_subdag else using_start_date
        while next_run_date and next_run_date <= using_end_date:
            run_dates.append(next_run_date)
            next_run_date = self.following_schedule(next_run_date)
        return run_dates
    def normalize_schedule(self, dttm):