feat: initial commit

[zachsmith1]

ExternalDNS webhook provider that manages DNS records through Datum Cloud's DNS custom resources (DNSZone and DNSRecordSet). The webhook runs as a sidecar container alongside ExternalDNS and translates its endpoint change requests into Kubernetes CRDs managed by the dns-operator.

The webhook implements the ExternalDNS webhook provider protocol (/, /records, /adjustendpoints) and:

• Discovers zones by watching DNSZone resources across the cluster with periodic refresh
• Routes records to the correct zone using longest-suffix domain matching
• Tracks ownership via external-dns.io/owner labels to prevent conflicts between instances
• Filters domains so ExternalDNS only attempts to manage hostnames that match a known zone

Multi-cluster zone sources

For simple deployments, CLI flags configure a single in-cluster zone source:

--owner-id=my-instance --namespace=production

For multi-cluster setups, a YAML config file defines additional zone sources via --config:

zoneSources:
  - name: production
    kubeconfig: /etc/prod.kubeconfig
  - name: staging
    kubeconfig: /etc/staging.kubeconfig
    namespace: dns-zones