Add support for templating in on_failure_callback

[jroach-astronomer]

In reference to #206, add support for templating in on_failure_callback. Requester is specifically looking to support templated parameters that do not need to be stored in a .py file.

Here's an example (from the issue submitted by @matveykortsev) for reference:

from airflow.providers.slack.notifications.slack import send_slack_notification
'on_failure_callback': [
        send_slack_notification(
            slack_conn_id='slack',
            text="""
                :red_circle: Task Failed. 
                *Task*: {{ ti.task_id }}  
                *Dag*: {{ ti.dag_id }} 
                *Execution Time*: {{ ti.execution_date }}  
                *Log Url*: {{ ti.log_url }} 
                """,
            channel="analytics-alerts",
            username="Airflow",
        )
    ],

@pankajastro has created an issue (#200) to ensure consistency between native Airflow and dag-factory.

[jroach-astronomer]

This would be a new feature, I'm going to see if it's something that's feasible. Basically, we'd need to support functionality that looks like this:

<dag-id>:
  default_args:
    on_failure_callback: <path-to-function>
      <arg-name>: value
      <arg-name>: value

[matveykortsev]

Hi guys, is there any eta for this release?

[jroach-astronomer]

@matveykortsev, there is currently a Pull Request in review with a solution to this issue.

[matveykortsev]

@jroach-astronomer I see, there is not mention in PR so haven't seen this.
Thanks, cant wait for release!