Purpose
=======
Allow to group records by their property values,
like we can do with normal fields.
Technical
=========
Because there's no foreign key, when we group by a relational property
we need to check the existence of the ids in the query (and same for
selection and tags, because we might have value of a deleted
option / tag in database).
Task-3032464
Part-of: odoo/odoo#103510