OPAQUE (RFC 9807) implementation (using `opaque-ke` crate)
with opaque authentfication, server will never receive the password (in the auth=password mode)
this is a must have to create trust with users to permit end to end encryption in the future
(we cannot know if user use the same password/passphrase for his asymetric key or his oxicloud auth,
this is why server must never have the password)
pass1: prepare server
Edouard Vanbelle