social/mail_notification_custom_subject/security/ir.model.access.csv

1	id	name	model_id:id	group_id:id	perm_read	perm_write	perm_create	perm_unlink
2	access_mail_notification_custom_subject_user	mail_notification_custom_object	model_mail_message_custom_subject	base.group_user	1	0	0	0
3	access_mail_notification_custom_subject_admin	mail_notification_custom_object	model_mail_message_custom_subject	base.group_system	1	1	1	1