When a user is assigned as responsible of request, we want him to get a
mail saying that he's a assigned to this request, a standard behaviour
exists in Odoo to perform such a thing, which consist of having a field
named 'user_id' which is tracked, so to avoid overriding the method, we
renamed the field 'technician_user_id' in 'user_id'.
Wre also set teh mail subtype 'request create' with default false, to
have the same behaviour as the on in project, meaning that it is true
only if you have the parent subtype set to true.
TASK-ID: 58645