curl --request POST \
  --url https://api.us.lexful.app/v1/entity_types/{entityTypeIdOrName}/references/{referenceName} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --header 'X-Account-ID: <api-key>' \
  --data '
{
  "name": "<string>",
  "target_entity_types": [
    "<string>"
  ],
  "display_name": "<string>",
  "required": true,
  "multiple": true
}
'

{
  "name": "<string>",
  "display_name": "<string>",
  "required": true,
  "multiple": true,
  "description": "<string>",
  "target_entity_types": [
    "<string>"
  ],
  "validation_rules": {
    "min_count": 1,
    "max_count": 2,
    "bidirectional": true,
    "cascade_delete": true
  }
}