Implement Clone for AccountCredentials

[h33p]

Currently, AccountCredentials only implements Serialize, and Deserialize, but cloning them may be useful for recreating ACME client instances. We currently do the following under the hood:

fn clone_creds(creds: &AccountCredentials) -> AccountCredentials {
    serde_json::from_str(&serde_json::to_string(&creds).unwrap()).unwrap()
}

However, I feel like this is unnecessary, and it would be better to be able to just clone the creds.

[djc]

Why do you need to clone the credentials? What's the use case?

[h33p]

Why do you need to clone the credentials? What's the use case?

Whenever I need to recreate Account.

Account::from_credentials consumes the credentials object. Sometimes, ACME server returns an error when acquiring a session, and thus, a retry is needed. Alternatively, I experienced a case where the account session stopped working after some time, which could be fixed by recreating the Account object, which once again, requires me to clone the credentials.

[djc]

Okay, I'd rather fix the cases where you need to recreate an account. It is on purpose that there's no Clone implementation for AccountCredentials, in order to make it harder to accidentally leak private key data.