[SECURITY] Notify users about account security changes

- Currently if the password, primary mail, TOTP or security keys are
changed, no notification is made of that and makes compromising an
account a bit easier as it's essentially undetectable until the original
person tries to log in. Although other changes should be made as
well (re-authing before allowing a password change), this should go a
long way of improving the account security in Forgejo.
- Adds a mail notification for password and primary mail changes. For
the primary mail change, a mail notification is sent to the old primary
mail.
- Add a mail notification when TOTP or a security keys is removed, if no
other 2FA method is configured the mail will also contain that 2FA is
no longer needed to log into their account.
- `MakeEmailAddressPrimary` is refactored to the user service package,
as it now involves calling the mailer service.
- Unit tests added.
- Integration tests added.

routers/web/user/setting/account.go

@@ -104,7 +104,15 @@ func EmailPost(ctx *context.Context) {
 
 	// Make emailaddress primary.
 	if ctx.FormString("_method") == "PRIMARY" {
-		if err := user_model.MakeEmailPrimary(ctx, &user_model.EmailAddress{ID: ctx.FormInt64("id")}); err != nil {
+		id := ctx.FormInt64("id")
+		email, err := user_model.GetEmailAddressByID(ctx, ctx.Doer.ID, id)
+		if err != nil {
+			log.Error("GetEmailAddressByID(%d,%d) error: %v", ctx.Doer.ID, id, err)
+			ctx.Redirect(setting.AppSubURL + "/user/settings/account")
+			return
+		}
+
+		if err := user.MakeEmailAddressPrimary(ctx, ctx.Doer, email, true); err != nil {
 			ctx.ServerError("MakeEmailPrimary", err)
 			return
 		}