Add more info to doc string
factor out base test class and be explicit about what status code is expected
Prep tests for transactions and add new test case for creating a zone on top of another zone
refactor create_zone function to use tranransactions and to allow creation of zones on top of an existing zone
since an SOA is assinged to nameserver records before they are created in the new `create_zone`, we now see incremental build tasks being created