vivso-suboptions not properly supported in Netconf

An example of configuration of vivso-suboptions is shown in the ARM (simplified here):

"Dhcp4": {
    "option-data": [
        {
            "name": "vivso-suboptions",
            "space": "dhcp4",
            "data": "2234"
        },
        {
            "name": "vivso-suboptions",
            "space": "dhcp4",
            "data": "3561"
        },
        ...
    ]
}

In the Kea yang definition found in: src/share/yang/modules/kea-dhcp4-server@2023-06-28.yang the keys are "code space" as shown here:

  grouping option-data-list {
    description "Option data list grouping.";
    list option-data {
      key "code space";
      description "Option data entry.";
      leaf code {
        type uint8;
        mandatory true;
        description "Option code.";
      }
      leaf space {
        type string;
        mandatory true;
        description "Option space.";
      }
      uses dhcp:option-data-name;
      uses dhcp:option-data-data;
      uses dhcp:option-data-csv-format;
      uses dhcp:option-data-always-send;
      uses dhcp:option-data-never-send;
      uses dhcp:option-data-user-context;
    }
  }

which makes it impossible to create two option-data entries with the same space (dhcp4) and code (125 for VIVSO). This is as stated in RFC6020:

The combined values of all the leafs specified in the key are used to uniquely identify a list entry. All key leafs MUST be given values when a list entry is created.

So this sysrepocfg xml works:

<config xmlns="urn:ietf:params:xml:ns:yang:kea-dhcp4-server">
  <subnet4>
    <id>1</id>
    <pool>
      <start-address>192.168.20.100</start-address>
      <end-address>192.168.20.200</end-address>
    </pool>
    <subnet>192.168.20.0/24</subnet>
  </subnet4>
  <option-data>
    <code>125</code>
    <space>dhcp4</space>
    <data>2234</data>
  </option-data>
  <interfaces-config>
    <interfaces>enp0s3</interfaces>
  </interfaces-config>
  <control-socket>
    <socket-name>/tmp/kea-dhcp4-ctrl.sock</socket-name>
    <socket-type>unix</socket-type>
  </control-socket>
</config>

while this, with second entry for option 125, does not:

<config xmlns="urn:ietf:params:xml:ns:yang:kea-dhcp4-server">
  <subnet4>
    <id>1</id>
    <pool>
      <start-address>192.168.20.100</start-address>
      <end-address>192.168.20.200</end-address>
    </pool>
    <subnet>192.168.20.0/24</subnet>
  </subnet4>
  <option-data>
    <code>125</code>
    <space>dhcp4</space>
    <data>2234</data>
    <code>125</code>
    <space>dhcp4</space>
    <data>3561</data>
  </option-data>
  <interfaces-config>
    <interfaces>enp0s3</interfaces>
  </interfaces-config>
  <control-socket>
    <socket-name>/tmp/kea-dhcp4-ctrl.sock</socket-name>
    <socket-type>unix</socket-type>
  </control-socket>
</config>

When an attempt to apply the configuration is made, the output is as follows:

$ sudo sysrepocfg -v debug -d startup -f xml -m kea-dhcp4-server --edit=startup4.xml
[INF] Connection 52 created.
[INF] Session 20 (user "root", CID 52) created.
libyang error: Invalid position of the key "code" in a list. (Data location "/kea-dhcp4-server:config/option-data[code='125'][space='dhcp4']/code", line number 14.)
sysrepocfg error: Data parsing failed
[INF] No datastore changes to apply.

Please see SF1556 for further details including some proposed solutions.