Document exercising DNS Failover via groups

[philbrookes]

how does a user failover between DNS Groups:

• Add new active group to the active-groups TXT record.
  • Inactive records recheck this value every 15 seconds currently.
• Remove the old active group from the active-groups TXT record.
• Confirmation via DNSRecord status in a now active cluster.
  • Active: true
  • Ready: true
  • compare Group value to ActiveGroups value.
• Confirm zone is updated correctly.

Interesting related information:

• Changing the active groups is not an event that triggers a reconcile, failover will happen on the next scheduled reconcile of a now active cluster.