Subscription intent public error

When a subscription intent fails, the public_error attribute on the Subscription Intent object identifies the cause. Fintoc uses the following public_error values. Handle unknown values because Fintoc can add new errors.

`public_error`	Description
`account_type_not_permitted`	The selected account type is not allowed for this enrollment.
`authorization_timeout`	Your customer did not authorize the direct debit enrollment in time.
`bank_connection_error`	Fintoc had a problem connecting with the selected bank.
`bank_not_available`	The selected bank is temporarily unavailable.
`internal_error`	An unexpected error occurred while processing the enrollment.
`login_credentials_locked`	The bank locked your customer’s credentials after too many failed attempts.
`login_invalid_credentials`	The bank credentials your customer entered are incorrect.
`mfa_authorization_timeout`	Your customer did not complete the bank’s multi-factor authentication in time.
`mfa_unavailable`	The bank’s multi-factor authentication is not available for your customer.
`password_change_required`	The bank requires your customer to change their password before continuing.
`request_timeout`	The request to the bank timed out.
`subscription_intent_expired`	The subscription intent expired before your customer completed the enrollment.
`user_left`	Your customer left the widget before completing the enrollment.