Implement the DeadlineAlerts Interface class and DeadlineAlerts.DAGRUN_LOGICAL_DATE

[ferruzzi]

Implement the DeadlineAlerts class using a builder model and the first "type" of DeadlineAlert with thorough test coverage.

[rawwar]

@ferruzzi , I just checked code and don't see any references to "DAGRUN_EXECUTION_DATE". Was this accidentally marked completed?

It is. Its called "DAGRUN_LOGICAL_DATE"