can't set a default password in a createOptionForm()

Hi to everyone! I am trying to autogenerate a password from a createOptionForm (a user creation form inside another resource) once a user fills a form (my form creates a pet and an user at the same time), with the first 3 letters of his name and the first 3 numbers of his phone number. The problem is that I don't know how to do it because I have to wait for the user to fill the form and click on submit to do this. With afterStateUpdated it does not work. I just want the password to be generated automatically in this form, so adding this in the “edit” resource with beforeCreate() is not an option. All the time i get the error: local.ERROR: SQLSTATE[HY000]: General error: 1364 Field 'password' doesn't have a default value . I attach my code. Thanks in advance