curl --request POST \
  --url https://us.api.flexprice.io/v1/integrations/link \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '
{
  "entity_id": "<string>",
  "entity_type": "customer",
  "provider_entity_id": "<string>",
  "provider_type": "<string>",
  "metadata": {}
}
'

{
  "mapping": {
    "created_at": "2023-11-07T05:31:56Z",
    "created_by": "<string>",
    "entity_id": "<string>",
    "entity_type": "customer",
    "environment_id": "<string>",
    "id": "<string>",
    "provider_entity_id": "<string>",
    "provider_type": "<string>",
    "status": "published",
    "tenant_id": "<string>",
    "updated_at": "2023-11-07T05:31:56Z",
    "updated_by": "<string>"
  }
}