add resource for IPv6 DHCP Configuration

[jkliss-csco]

For DHCP in IPv6 scenario there are a few providers missing:

Example Config:
SERVER CONFIG:

ipv6 local pool DHCPv6-PD 2000::/56 64

ipv6 dhcp pool DHCPv6-PD
  prefix-delegation pool DHCPv6-PD
  dns-server 2001:4860:4860::8888
  dns-server 2001:4860:4860::4444
  domain-name [test.local](https://test.local/)
  vendor-specific 9
  suboption 1 address 2001:DB8:CAFE::1
!
interface GigabitEthernet1
  no ip address
  negotiation auto
  ipv6 address 2001::1/64
  ipv6 enable
  ipv6 dhcp server DHCPv6-PD
end

CLIENT CONFIG:

interface GigabitEthernet1
  no ip address
  negotiation auto
  ipv6 dhcp client pd ISP_PREFIX
  ipv6 address autoconfig default
  ipv6 enable
  end

[jkliss-csco]

This will require in my understanding:

/Cisco-IOS-XE-native:native/interface/<INTERFACE_TYPE>/ipv6/address/dhcp

/Cisco-IOS-XE-native:native/ipv6/local/pool
/Cisco-IOS-XE-native:native/ipv6/local/pool/group
/Cisco-IOS-XE-native:native/ipv6/local/pool/id
/Cisco-IOS-XE-native:native/ipv6/local/pool/last
/Cisco-IOS-XE-native:native/ipv6/local/pool/prefix-length
/Cisco-IOS-XE-native:native/ipv6/local/pool/start
/Cisco-IOS-XE-native:native/ipv6/local/pool/start-address

/Cisco-IOS-XE-native:native/ipv6/dhcp
/Cisco-IOS-XE-native:native/ipv6/dhcp-relay

Please reach out if further info is necessary.

---

My findings so far:

From Cisco-IOS-XE-interfaces.yang:

      container dhcp {
        description
          "IPv6 DHCP interface subcommands";
        status obsolete;
      }
      container address {
        description
          "Configure IPv6 address on interface";
        status obsolete;
        container dhcp {
          description
            "Obtain IPv6 address from DHCP server";
          status obsolete;
          presence "true";
          leaf rapid-commit {
            description
              "rapid-commit for prefix delegation";
            status obsolete;
            type empty;
          }
        }

From Cisco-IOS-XE-dhcp.yang > ipv6/local/pool

        container pool {
          description
            "IPv6 prefix pool";
          leaf pool-name {
            description
              "IPv6 prefix pool";
            type string {
              length "1..512";
            }
          }
     leaf-list dns-server {
        description
          "Server's name or IPv6 address";
        ordered-by user;
        must 'not(../import/dns-server)' {
          error-message "Both Static and Import DNS-Server cannot be configured at the same time.";
        }
        type union {
          type inet:ipv6-address;
          type string;
        }
      }
      leaf-list domain-names {
        ordered-by user;
        must 'not(../import/domain-name)' {
          error-message "Both Static and Import Domain-name cannot be configured at the same time.";
        }
        description
          "Domain name to complete unqualified host names";
        type string;
      }
      leaf domain-name {
        status deprecated;
        description
          "Domain name (DEPRECATED) to complete unqualified host names";
        type string;
      }
        leaf-list domain-name {
          description
            "NIS server domain name";
          ordered-by user;
          type string;
          must 'not(../../import/nis/domain-name)' {
            error-message "Both Static and Import NIS-Domain-name cannot be configured at the same time.";
          }
        }
      }
        leaf dns-server {
          description
            "Import DNS address";
          type empty;
        }
        leaf domain-name {
          description
            "Import Domain name option";
          type empty;
        container interface {
          status obsolete;
          description
            "Specify interface to import options from";
          uses ios-ifc:interface-obsolete-grouping;
        }
      }
      list link-address {
        description
          "Link-address to match";
        key "address";
        leaf address {
          type ios-types:ipv6-prefix;
        }
      }
      container option {
        description
          "DHCPv6 Options configuration";
        leaf include-all {
          description
            "Include all DHCPv6 configured options in REPLY";
          type empty;
        }
      }
      list vendor-specific {
        description
          "Configure Vendor-specific option";
        key "value";
        leaf value {
          description
            "Enterprise ID";
          type uint32 {
            range "1..4294967295";
          }
        }
          leaf address {
            description
              "IPv6 address";
            type inet:ipv6-address;
          }
          leaf ascii {
            description
              "ASCII string";
            type string;
          }
          leaf hex {
            description
              "Hex string";
            type string {
              pattern '[0-9a-fA-F]*' {
                error-message "Incorrect format";
              }
            }
          }
        }
      }
    }