Create Kerberos Descriptor Resource to be accessed via the REST API

Create Kerberos Descriptor Resource to be available via REST API such that the resource is made available as

• A sub-resource to a Stack Version resource
  • Default Kerberos descriptor (with full hierarchy) for the requested Stack Version, read from kerberos.json files in relevant stack definition
• A sub-resource to a Stack Service resource
  • Default Kerberos descriptor for the requested Stack Service, read from kerberos.json file in relevant service definition
• A sub-resource to a Cluster resource
  • Actual Kerberos descriptor for the requested Cluster (full hierarchy, pulled from Ambari database, declared when enabling Kerberos)
• A sub-resource to a Service resource
  • Actual Kerberos descriptor for the requested Service (pulled from Ambari database, declared when enabling Kerberos)

The Kerberos descriptor is to be set when when enabling Kerberos on the cluster. The cluster update PUT request is to contain a kerberos_descriptor block. This data is parsed into a org.apache.ambari.server.state.kerberos.KerberosDescriptor and used to update the org.apache.ambari.server.state.kerberos.KerberosDescriptor created from the stack definition.

The resulting Kerberos Descriptor is used to enable Kerberos and should be stored in the Ambari database to be recalled as necessary:

• When the resource is requested
• When a new host or service is added to the cluster