Util classes

Friends,

I am working now in a Grails 4 project with IntelliJ Idea Community IDE. I imported a project created from the command line as a Gradle Project.

I am trying to add into my project two util criptography classes. These groovy classes do not have anything to do with Controllers, Services nor Domain, so I did not execute in the terminal grails create domain, grails create controller.

I tried to import my two util groovy classes in the project structure, but I can't import them. I receive a message from the terminal saying

unable to resolve class br.gov.cmb.cmbiddocumentproperties.utils.AesCipher
@ line 5, column 1.
import br.gov.cmb.cmbiddocumentproperties.utils.AesCipher

Could anyone help me to add these classes into my project?

Thanks