@Hugh-Bao There are no specific guidelines, only specification which is fully implemented. Yes, you can use one "eventURL" for all subscriptions.
Yes, you can with postman test the C2C in a way that pluggedin.cloud is a target cloud. But you want be able to receive events with postman. For that you need another tool. e.g. https://ptsv2.com/
@kwlodarczyk subscription retrieval API will be released in next spec release cycle. Another way how you can clean it up - reply 4xx to received event. Particular subscription should be then canceled. Do we have this implemented @jkralik ?
@kwlodarczyk @ondrejtomcik You need to return http code 410 (StatusGone ) to remove subscription.