Add NexusUser CRD

[andykrohg]

• Leverage devsecops-api-collection to create new users (this requires an enhancement)
• Should take parameters for
  • Realm (Local, Rut Auth)
  • User Info (first/last name, username, email)
  • Level of Privilege (Admin, Read, Write)
• Include Molecule test
• Update/reassess list of adminusers on Nexus CR

[andykrohg]

WIP here: https://github.com/david-rh/nexus-operator