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
"""Table containing DAG properties"""
    __tablename__ = "dag"
    """
    These items are stored in the database for state related information
    """
    dag_id = Column(String(ID_LEN), primary_key=True)
    root_dag_id = Column(String(ID_LEN))
    
    
    is_paused_at_creation = conf.getboolean('core', 'dags_are_paused_at_creation')
    is_paused = Column(Boolean, default=is_paused_at_creation)
    
    is_subdag = Column(Boolean, default=False)
    
    is_active = Column(Boolean, default=False)
    
    last_parsed_time = Column(UtcDateTime)
    
    last_pickled = Column(UtcDateTime)
    
    
    last_expired = Column(UtcDateTime)
    
    scheduler_lock = Column(Boolean)
    
    pickle_id = Column(Integer)