Did you know you can use Grails' domain classes without GORM and benefit nonetheless from functionality such as RestfulController. Great post by @mrhaki.
With CF CLI command line utilities or with a Gradle task, the deployment of a Grails 3 app to PWS is easy.
We plan to add more deployment guides to Grails Guides.
@burtbeckwith's talk at GR8Conf India. He warns about the use of hasMany in Grails applications. He explains how to avoid those traps and avoid performance problems in the future.
@mr_paul_woods shows a hands-on migration from hasMany traditional model to hasMany free world.
I personally like to keep my domain models anemic. Thus, I would move the getItems and deletion logic to a service.