Purpose ======= A field `use_google_gmail_service` has been used in stable to define a mail server which use Gmail authentication. But now that the fields `smtp_authentication` exists, we want to use it to simplify the mail server form view. For the incoming mail server, the field `server_type` will be used for the same purpose. Add a new field to have the option to install `google_gmail` in the main settings page. Task-2170676 closes odoo/odoo#83413 Related: odoo/upgrade#3199 Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>