I couldn't find any official documentation specifying what each parameter to a `sla_miss_callback` callable are. This would be a great addition to know how to properly format the messages sent.
airflow/models/dag.py
self,
        earliest: Optional[pendulum.DateTime],
        latest: pendulum.DateTime,
        *,
        align: bool = True,
    ) -> Iterable[DagRunInfo]:
        """Yield DagRunInfo using this DAG's timetable between given interval.
        DagRunInfo instances yielded if their ``logical_date`` is not earlier
        than ``earliest``, nor later than ``latest``. The instances are ordered
        by their ``logical_date`` from earliest to latest.
        If ``align`` is ``False``, the first run will happen immediately on
        ``earliest``, even if it does not fall on the logical timetable schedule.
        The default is ``True``, but subdags will ignore this value and always
        behave as if this is set to ``False`` for backward compatibility.
        Example: A DAG is scheduled to run every midnight (``0 0 * * *``). If
        ``earliest`` is ``2021-06-03 23:00:00``, the first DagRunInfo would be
        ``2021-06-03 23:00:00`` if ``align=False``, and ``2021-06-04 00:00:00``
        if ``align=True``.
        """
        if earliest is None:
            earliest = self._time_restriction.earliest