Support for NS1 Managed DNS

[somaritane]

Consider adding Support for NS1 edgeDNS, as further step to promote k8gb in community.

• NS1 is supported provider by external-dns, we should be able to utilize external-dns capabilities for zone delegation without the need for direct API calls
• Split-brain control support is out of the scope until we have more consolidated approach on split-brain management.
• NS1 provider needs NS1_APIKEY token to wired to external-dns Deployment as environment variable.

[ytsarev]

Implemented by https://github.com/AbsaOSS/k8gb/pull/217