Make non-ignorable SSL errors explicit
So far this is done implicitly in KSSLD by not being able to persist
these error codes in its config file. This however is rather error
prone, and requires manual enum <-> string mapping there.
Now we do this explicitly, which allows us to eventually use QMetaEnum
for serialization in KSSLD.
Reviewers: Frameworks, apol
Reviewed By: apol
Subscribers: apol, kde-frameworks-devel
Maniphest Tasks: T11620
Differential Revision: https://phabricator.kde.org/D24742