Foreman » Smart Proxy

Refs #12209: Pass in the actual values to {create,remove}_ptr_record

Fixes #12597: remove extraneous method definition in the DNS API tests

And removed redundant validation in dns api 'delete' call

Fixes #12209: introduced basic support for di in dns module

DNS record class interface has been cleaned up with validation and type
parsing logic moved into the controller layer, resulting in separate
create and delete methods for A and PTR records.

Fixes #7008: dns providers are now plugins

fixes #7352 - missing DNS record returns 404

fixes #6722 - correct require for kerberos utilities

fixes #6588 - don't load user settings when testing default settings

Fixes #4866: Breaking up monolithic smart-proxy into modules