On Forge 1.x you could add constraints to a specific field with

constraint NotNull --onProperty login ;

The constraint commands are missing. If we follow the new naming convention, we should have, at least, one command to create new custom constraints (that could go into a default constraint package for example :

constraint-new MyOwnConstraint ;

And a command to add a constraint to a property :

constraint-add NotNull --onProperty login ;
constraint-add MyOwnConstraint --onProperty lastname ;