Expecting a doc showing guidance on what other data should be persisted by a controller

[yunxi-zhang]

As we only want necessary data to be persisted to an ACA-Py's wallet/db storage, it's better to have a doc available somewhere contributed by any experienced teams who show a guidance on what type of data should be handled by a controller to be persisted to somewhere else, so the wallet will always have the necessary data such as credentials, private DID.