mail_activity_done

Ensure completed mail activities remain stored for reporting by enabling the keep done option across all activity types.

Key Features

mail.activity.type: Defaults keep_done to true on new activity types so completed activities are retained instead of being removed.
mail.activity.type: Post-install configuration activates keep_done on all existing activity types to keep finished activities available.
mail.activity: Migration archives done activities that were left active and flags archived ones not marked done to align their status with Odoo 18.0 behavior.