PasswordProtectedKeyAllowedCredential

A key pair whose private half the client keeps encrypted under their own password. Unlike the
other mechanisms this one cannot be answered from the identifier alone - the encrypted key has to
travel with the challenge, which is why the provider always puts it in this section and why it is
required here.

{
    "kind": "passwordProtectedKey",
    "id": "string",
    "encryptedPrivateKey": "string"
}