[FIX] mail: escape RegExp pattern
[FIX] mail: escape RegExp pattern

to prevent crashes if the user types, e.g. a \, in the partner's autocompletes
in Discuss ('Add a DM' in sidebar and 'Invite people to channel' dialog).

dfang/odoo,dfang/odoo,dfang/odoo,hip-odoo/odoo,ygol/odoo,ygol/odoo,ygol/odoo,dfang/odoo,dfang/odoo,hip-odoo/odoo,hip-odoo/odoo,ygol/odoo,hip-odoo/odoo,ygol/odoo,hip-odoo/odoo,ygol/odoo,dfang/odoo,hip-odoo/odoo,ygol/odoo