PURPOSE
Allow alias domains to be multiple, notably to be used in a multi company
environment where each company has its own alias domain.
SPECIFICATIONS
As 'alias_domain' is now dynamic and not based on a configuration parameter
it makes sense to be able to change it when having several alias domain.
We now allow writing on 'alias_domain_id' in 'mail.alias.mixin(.optional)'.
Users may now change the alias domain of the alias coming with the mixin
when they have write access on the record.
Task-36879 (Mail: Support Multi Domains Aliases)
Part-of: odoo/odoo#76734