Should not assume that a participant pico opting out is a child pico of the main pico

[b1conrad]

Instead, the rule that triggers on the opting out event needs to delete the pico in a more general way.

[b1conrad]

The principal work of the rule is to use the person_id (passed in from the Opt Out form) to find the ECI of the participant pico.

This bears more looking into. The request must come using the same ECI that that participant uses to contact the list pico. Oh, but that is the same for every participant and shouldn't be! (Hence, issue #83)