v1.1.0 of malipo

Official Flutter/Dart SDK for the Malipo Payment Gateway. Securely accept Mobile Money payments (Vodacom MPesa, Orange Money, Airtel Money) in the DRC. Changelog excerpt: - Added support for Refunds API: Initiate full or partial refunds for successful transactions. - Added support for Hosted Checkout Sessions: Programmatically create hosted payment links for dynamic checkout flows. - Updated MalipoTransactionto include settlement fields and the declinedstatus. - Added new models: MalipoRefund, RefundCreateParams, MalipoCheckoutSession, and CheckoutSessionCreateParams.