* Restructure controller and res.users logic to prevent RPC authentication for
users with MFA enabled and add support for multiple simultaneous MFA sessions
* Switch trusted device cookies from using the DB secret to user-level secret
keys, thereby increasing security
* Remove MFA login tokens and trusted device model, which are now redundant
* Add migration logic that generates a trusted device cookie key for every user
with MFA enabled and cleans up device model ir records to prevent warnings
* Update unit tests and remainder of module accordingly
* Add relevant fields and methods to the res.users model
* Overload check_credentials in res.users to allow for logins using an MFA
login token rather than a password
* Add the res.users.authenticator and res.users.device models, along with
appropriate ACLs and record rules
* Add the res.users.authenticator.create wizard model and an associated view
to facilitate creation of res.users.authenticator records
* Extend base.view_users_form_simple_modif with fields needed to manage the
new functionality
* Add an AuthTotp controller that inherits from Home in the web module and an
associated view to introduce MFA logic to the login process
* Add several new exception classes that inherit from AccessDenied
Oleg Bulkin