when sync'ing users make sure the user's remoteid matches the remote issuing the update (#27203)

server/platform/services/sharedchannel/util.go

@@ -148,3 +148,10 @@ func reducePostsSliceInCache(posts []*model.Post, cache map[string]*model.Post)
 	}
 	return reduced
 }
+
+func SafeString(p *string) string {
+	if p == nil {
+		return ""
+	}
+	return *p
+}