Some configuration options can take space separated strings; for
example `SSLVersions` can be configured with multiple allowed
versions.
SSLVersions TLSv1.3 TLSv1.2
This can now be represented in Home Manager.
SSLVersions = [ “TLSv1.3” “TLSv1.2” ];
In implementing this change, it uses oneOf for config type, as it is a
cleaner way to represent the union than the nested eithers
formulation.
Also add SSLVersions to test lists of strings in
`account.extraConfig`.