This commit proposes to limit cache invalidation at some cases that will
trigger some behavior change when dealing with mail messages :
* creating messages linked to a document;
* update model or res_id of a message;
* updating notifications, as notified people could change some computed
fields on the record;
This commit also invalidates only mail-related fields as updating messages
should not invalidate other things than some computed fields linked to
mail.
Thibault Delavallée
9f3889eba3