**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/api_connexion/schemas/task_instance_schema.py
"""Schema for handling the request of clearing task instance of a Dag"""
    dry_run = fields.Boolean(default=True)
    start_date = fields.DateTime(missing=None, validate=validate_istimezone)
    end_date = fields.DateTime(missing=None, validate=validate_istimezone)
    only_failed = fields.Boolean(missing=True)
    only_running = fields.Boolean(missing=False)
    include_subdags = fields.Boolean(missing=False)
    include_parentdag = fields.Boolean(missing=False)
    reset_dag_runs = fields.Boolean(missing=False)
    @validates_schema
    def validate_form(self, data, **kwargs):
        """Validates clear task instance form"""
        if data["only_failed"] and data["only_running"]:
            raise ValidationError("only_failed and only_running both are set to True")
        if data["start_date"] and data["end_date"]:
            if data["start_date"] > data["end_date"]:
                raise ValidationError("end_date is sooner than start_date")
class SetTaskInstanceStateFormSchema(Schema):
    """Schema for handling the request of setting state of task instance of a DAG"""
    dry_run = fields.Boolean(default=True)
    task_id = fields.Str(required=True)
    execution_date = fields.DateTime(required=True, validate=validate_istimezone)
    include_upstream = fields.Boolean(required=True)
    include_downstream = fields.Boolean(required=True)
    include_future = fields.Boolean(required=True)
    include_past = fields.Boolean(required=True)
    new_state = TaskInstanceStateField(required=True, validate=validate.OneOf([State.SUCCESS, State.FAILED]))
class TaskInstanceReferenceSchema(Schema):