[feature] Implement soft_delete and stop_soft_delete flags in the plan

[philbrookes]

Some useful DNS Records for local testing (will require some tweaking e.g. hostnames): https://gist.github.com/philbrookes/617e03b739f43f01423f9ea94284333d

To test having one or more removed, edit the following:

    - dnsName: cluster1-gw1-ns1.klb.loadbalanced.pb.hcpapps.net
      recordTTL: 60
      recordType: A
      targets:
        - 172.18.200.1

To look like:

    - dnsName: cluster1-gw1-ns1.klb.loadbalanced.pb.hcpapps.net
      recordTTL: 60
      recordType: A
      targets:
        - 172.18.200.1
      labels:
        soft_delete: "true"

• mark cluster1 or cluster2 individually for removal, to see it removed.
• mark cluster3 for removal and it will not remove (only record in the GEO)
• mark cluster1 for removal, then afterwards cluster2 and see cluster1 removed but not cluster2 (last record in GEO).

As discussed, this will not cover removing the label on cluster1 and cluster2 simultaneously (i.e. race conditions) that will be covered in future work: #385

[maksymvavilov]

Looks good. Great work!