Create an end user entity

curl --request POST \
  --url https://app.herondata.io/api/end_user_entities \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '{
  "display_order": 123,
  "entity_description": "<string>",
  "entity_name": "<string>",
  "is_list": true
}'

{
  "display_order": 123,
  "entity_description": "<string>",
  "entity_name": "<string>",
  "heron_id": "<string>",
  "is_list": true
}