How to notify by email only the users concerned

@Francewhoa, this is a note to myself

Related comment and front end screenshots about a frequent challenge about the present need for more documentation about Gitea email notification. Including, but not limited to, activate email notification, or deactivate, or allowing each user to decide if they need notification at https://forum.gitea.com/t/gitea-is-not-sending-notifications/6308/5