text: alter table users add firstname varchar(255) null,
                    add lastname varchar(255) null,
                    add login varchar(255) null;
  update users set firstname='', lastname='', login='';
  alter table users alter column firstname set not null,
                    alter column lastname set not null,
                    alter column login set not null;
  
  alter table users rename column login to username;
  alter table users add passwordsha256 varchar(255) null;
  update users set passwordsha256='';
  alter table users alter column passwordsha256 set not null;
  