Constants in the foreighn key constraints

[aleksey ksenzov <alekseyksenzov@xxxxxxxxx>]

Hi team.
Latest time we faced several issues which wouldn't arise provided we have possibility to use constants in foreign key constraints.
brief example where it would be helpful:

table_a
( id uuid,
parent_id uuid,
is_deleted boolean

)
having possibility of FK (parent_id, false) to (id, is_deleted)
would disallow setting parent record deleted flag to true if they have children, or insert record with is_deleted = true parent.

Regards,
Aliaksei.