There are some cases where we want to allow users to autenticate without any password. For example this will be usefull for development environment or public demo servers.
Implement a trust login method, that returns the valid id if the user exists on the database without checking anything else.
This option should be disabled by default and we should document that is not encouraged to use it on production systems, as it is done for example in the PostgreSQL Documentation
Although this can be implemented by a third party module, I think it's interesting to add it on the trytond server basically to give a good advice that this is not encouraged to run this method on production systems.
I also propose to use this authentication method on the demo server.