grm(portal): should a household member see the household grievance in the portal?

[gonzalesedwin1123]

PR #415's portal rule scopes spp.grm.ticket to partner_id == user.partner_id. Core portal patterns often use ('partner_id', 'child_of', user.commercial_partner_id.ids). A grievance filed for a group/household registrant is invisible to the filing member's own portal login under the strict rule.

Product decision needed: is that intended (grievances are personal), or should household membership grant portal visibility? If the latter, the domain needs the registry's group-membership shape (spp.group.membership), not commercial_partner_id — the commercial-partner notion doesn't map to registrant households.

Raised from the PR #415 review thread on spp_grm/security/rules.xml:119.