MM-58255 Ensure remote users do not get valid email addresses (#27421)

* remote users don't get valid email addresses; remote users cannot have access tokens

* block notification emails for remote users

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/notification.go

@@ -1102,8 +1102,8 @@ func max(a, b int64) int64 {
 }
 
 func (a *App) userAllowsEmail(c request.CTX, user *model.User, channelMemberNotificationProps model.StringMap, post *model.Post) bool {
-	// if user is a bot account, then we do not send email
-	if user.IsBot {
+	// if user is a bot account or remote, then we do not send email
+	if user.IsBot || user.IsRemote() {
 		return false
 	}