dns/ddclient: Provider DNSExit - Cannot specify 'zone' field needed when hostname != zone

[jortkoopmans]

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• I have read the contributing guide lines at https://github.com/opnsense/plugins/blob/master/CONTRIBUTING.md
• I have searched the existing issues --> following up on closed dns/ddclient: fix needed for dnsexit provider's json for hostnames updates #3712
• The title contains the plugin to which this issue belongs

Describe the bug
This is a duplicate of closed #3712 . Reopening that ticket is also OK (and closing this one). The bug/issue is as described there.

Now following up on the previous bug report, as a ddclient version has been released that addresses it.
We could argue whether this is a pure bug, as the UI never supported the zone, so that is a feature request.

Recommended solution
Two things are needed imho:

• Adopt ddclient version that includes the fix for the proper zone handling for hostnames that are not equal to the zone (the root domain name the user registered). The best would probably be to adopt the latest and recent release v4.0.0. I just created a separate issue for this on the ports repo as this might involve some effort to handle breaking changes: [ddclient] Update to v4.0.0 (release) ports#223
• Implement the 'zone' field in the account configuration of opnsense for the ddclient plugin. It populates the same 'zone' config field as several other providers do.