List pico should give out a fresh ECI for each participant session

[b1conrad]

The ECI used now is too powerful to be given out to every participant.

Tagged byu-hr-oit
Event policy allows byu_hr_oit:*
Query policy allows byu.hr.oit/*

Suggest tagging the ECI generated for a session with both byu-hr-oit and the person ID and giving it a very restricted policy, to just the events and queries that it might need.

[b1conrad]

Event policy must allow
byu_hr_oit:opt_in
byu_hr_oit:person_deletion_request (type should be renamed opt_out for consistency?)

Query policy must allow
byu.hr.oit/index

Hm. When the participant logs in, we know already which of opt_in and opt_out would apply, so we could issue a channel permissioned accordingly.

[b1conrad]

With the person id in the tags of the session channel, we have a second witness to this id, to validate opting in/out operations.