Implement RMA export functionality and configuration settings

[dgoemans]

This pull request introduces a new RMA (Return Merchandise Authorization) export feature, allowing RMA data to be exported to an external Faslet backend. It adds configuration options for RMA export, implements the core export service, and enhances configuration interfaces and repositories to support these features.

RMA Export Feature Implementation

• Added the new ExportService class in Model/Rma/ExportService.php to handle exporting RMA entities to the Faslet backend, including payload building, event filtering, and webhook publishing.
• Introduced new configuration constants to RepositoryInterface for RMA export enablement, endpoint URL, auth token, timeout, and lifecycle events.
• Extended the RepositoryInterface with methods to get/set RMA export settings and check which lifecycle events should be exported.
• Implemented the new configuration methods in Model/Config/Repository.php, including secure retrieval and decryption of the RMA auth token, and logic for handling lifecycle events.

Configuration and Security Enhancements

• Updated BaseRepository to support decryption of sensitive config values (like the RMA auth token) by injecting and using EncryptorInterface. [1] [2] [3]
• Modified DataInterface and its implementation to allow fetching the shop ID for a specific store, improving multi-store support. [1] [2]