* Add Level27 DNS API support
Implements dns_level27_add and dns_level27_rm for the Level27 (level27.eu) DNS API, used for ACME dns-01 challenges.
- Authenticates with a persistent API key via the Authorization header.
- Resolves the registered zone with domains?filter and exact fullname match (supports DNS alias mode).
- Removes the challenge record by its exact TXT value, leaving other records intact (wildcard-safe).
- Optional LEVEL27_API override for non-default/staging endpoints.
* A little better documentation
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Co-authored-by: Jeroen Moors <jeroen.moors@level27.be>
