Creates an entity in your organization for the mode (live or test) of the API key used. An entity is a legal holder of accounts. The holder_id requirement depends on the entity country. For a Mexican entity (country_code is MX), holder_id is the Mexican tax ID (RFC) and is required. For a foreign entity (country_code other than MX), omit holder_id or send the generic foreign RFC XEXX010101000. Fintoc rejects any other value. A holder_id is unique within your organization, except the generic foreign RFC XEXX010101000, which can repeat across foreign entities.