[FR] A better and more explicit way to close and end firebase connection

**Is your feature request related to a problem? Please describe.**
After a few searchs I didn't find a way to properly close a connection with firebase . The API itself has this method "deleteApp" which disables the received firebase connection, but somehow this connection keeps active in memory, firebase docs (https://firebase.google.com/docs/reference/admin/node/firebase-admin.app.md#deleteapp) say it is the proper method to finish the connection locally, but also say it doesn't clean any "back end resource" which it is not clear.

**Describe the solution you'd like**
How about a method that really turns off the connection and clears the value of the client in memory.