Changes to Send an email

added the new errors/connection_limit_reached enum value to the type response property for the response status 422

added the new errors/not_supported_by_provider enum value to the type response property for the response status 422

added the new errors/password_reset_required enum value to the type response property for the response status 403

added the new optional header request parameter Idempotency-Key

added the non-success response with the status 409