Some models would like to use the 'mail.alias.mixin' but it creates an alias
for each record in the parent model. This leads to a lot of unused aliases
if only a subset of those records really use aliases i.e. a lot of aliases
with 'alias_name' being 'False'.
In this commit we introduce a new mixin 'mail.alias.mixin.optional' that
behaves like the old 'mail.alias.mixin' but without having the 'alias_id'
field required i.e. without the "inherits". When creating a record without
giving an 'alias_name' no alias is created.
In future commit, we plan to use it notably to remove custom code in account
journal model and make it more standard. Using it in more models will be done
later, but it is a candidate to cleanup unused aliases related to discuss
channel model.
Task-3453343 (Mail: Cleanup Alias Usage)
Prepares Task-36879 (Mail: Support MultiCompany Aliases)
Part-of: odoo/odoo#130632
Thibault Delavallée
1af84e28ee