API: Implement conditional rectification

API: Implement conditional rectification

This commit takes a lot of ideas and code from #3417 and subsequent
development and implements the following things:

 - Generate DNSSEC keys for a zone when "dnssec" is true in an API
   POST/PATCH for zones
 - Rectify DNSSEC zones after POST/PATCH when API-RECTIFY metadata is 1
 - Allow setting this metadata via the "api-rectify" param in a Zone
   object
 - Shows "nsec3param" and "nsec3narrow" in Zone API responses
 - Adds an "rrsets" request parameter for a zone to skip sending RRSets
   in the response (Closes #5712)

Closes #3417

Many thanks to Nils Wisiol (@nils-wisiol) for the initial
implementation.