* Added CAA support
* Fixed bind parsing of CAA records
* Added CAA parsing test
* Renamed CAA json fields
* Added CAA tag validation
* Updated CAA docs to clarify on the value field
* parse_tests: Fixed typo in caaflags
* Added integration test
* Small cleanups
* Integration tests: PTR tests should only happen if CanUsePTR
* Integration tests: SRE tests should only happen if CanUseSRV
* CanUseSRV should be validated early (in pkg/normalize/validate.go)
* CLOUDFLARE does not support SRV. Check for this during validation
* GCLOUD CanUsesRV (mostly by accident, but whatever works)
* Add support for SRV records for NAMEDOTCOM and ROUTE53.
* Improve docs
* Rename RR() to ToRR().
* Rename RecordConfig Priority to MxPreference (affects json IR data)
* WIP
* Enable PTR records in dnsconfig.js, in BIND provider.
* Rename REVERSE() to REV().
* More accurate PTR target checking
* Document REV()
* Fix broken test
