deltaspike-authorization (and maybe other quickstarts) contains a link to https://github.com/jboss-developer/jboss-wfk-quickstarts/blob/2.7.x-develop/README.md#add-an-application-user that is missing.

The right link should be pointed to https://github.com/jboss-developer/jboss-developer-shared-resources/blob/master/guides/CREATE_USERS.md#add-an-application-user