Optionalconfig: OathClientConfigOptional OATH client configuration.
A promise that resolves to an OathClient handle.
The factory is async because it calls the native create method to
initialise the OATH session and obtain an opaque handle string. Keep a
reference to the returned client and call OathClient.close when it is
no longer needed to release native resources.
OathError when the native OATH module fails to initialise.
Create a native-backed OATH client.