In order to achieve the task, the following changes were required:
* vectorize the base class for server attributes
* add a child class that enforces single-value attributes. It still
accepts/returns single-value lists in order to not break Liskov
substitution principle
* Existing attributes inherit from the child class
https://pagure.io/freeipa/issue/6937
Reviewed-By: Jan Cholasta <jcholast@redhat.com>
Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>
If a server attribute such as DNSSec Key master is unset, None is passed as
the attribute value into the upper API layers and displayed in the output of
`dnsconfig-show` et al. We should not show this and leave the attribute empty
instead.
https://fedorahosted.org/freeipa/ticket/5960
Reviewed-By: Pavel Vomacka <pvomacka@redhat.com>
Reviewed-By: Martin Basti <mbasti@redhat.com>