implemented experimental "consistent_publisher" option: /!\ pgsql schema needs to be updated /!\ New "consistent_publisher" option has been implemented to allow node owners + admins to modify an item while preserving the original publisher. This way, original publisher can still edit the item. In addition to `consistent_publisher`, `max_items` has been added to PGQSL schema to prepare for future implementation.

create table callbacks (
    service text not null,
    node text not null,
    uri text not null,
    PRIMARY KEY (service, node, uri)
);