API Integration Architecture for Secure Spain Integration

We are looking for a senior API Integration Architect to establish a reusable integration layer that connects our platform with external government/customs systems. The initial phase is a focused integration validation using Laravel/APIHub and Spain's AEAT platform. The work includes reviewing technical requirements, configuring the test environment, establishing certificate-based authentication and secure SOAP/WSDL connectivity, validating the AEAT Inbox list service (ListaDecV4), implementing a dedicated test interface with diagnostics and response validation, and structuring the integration for future development. The integration layer should build upon our existing middleware architecture rather than become a standalone, country-specific application. Relevant experience includes API integration architecture, Laravel/PHP, SOAP/XML web services, WSDL/XSD, certificate-based authentication (mTLS), external API integrations, and reliable integration design.