Add support for Netcup CloudDNS API Key Authentication

Welcome

• Yes, I'm using a binary release or the library within the two latest releases.
• Yes, I've searched for similar issues on GitHub and didn't find any.

Detailed Description

Netcup changed the Authentication type from

• Legacy-DNS: Legacy API Key und API-Passwort

to

• CloudDNS: API-Key

The legacy keys are currently used in the plugin, but should be changed in the future because of deprecation.

More information: https://www.netcup.com/de/helpcenter/dokumentation/domain/unsere-api

Used in NGINXPROXYMANAGER

Effective version of lego

latest

How do you use lego?

Other (please explain)

In which context are you using lego?

Personal use

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Confirmation

• Yes, I've included all the information above (version, usage, etc.).