Account should be able to be created from a key only

[axos88]

According to https://github.com/algesten/acme-lib/blob/5a4d55080635dc9a7f9a380a79984e8b5f9ab281/src/dir.rs#L117C9-L119C61

A call to newAccount is fine to do with an already existing key. The call will return the account url in this case.
This feature would allow users to only persist the account key (and the directory url if needed), and retrieve all necessary info from that.

[cpu]

According to https://github.com/algesten/acme-lib/blob/5a4d55080635dc9a7f9a380a79984e8b5f9ab281/src/dir.rs#L117C9-L119C61

I think a better citation for this is RFC 8555 7.3.1. In particular to do what you're describing it would be important to set the onlyReturnExisting bool to true in the new account request.

[axos88]

Thanks for that, submitting a PR soon