OpenCart Payment Extension Development (Compatible with OpenCart 3.x & 4.x)

We are looking for an experienced OpenCart developer to create a fully functional payment extension that replicates the same features and flow as the following

WooCommerce example:
https://github.com/paygate-to/WooCommerce-Instant-Payment-Gateway/blob/main/includes/class-paygatedotto-instant-payment-gateway-hostedpaygatedotto.php

The new OpenCart extension should integrate with the PayGate.to API (multi-provider mode) as described in the API documentation below:
https://documenter.getpostman.com/view/14826208/2sA3Bj9aBi

The final package should be cross-compatible and ready to install on both OpenCart 3.x and 4.x versions.

Deliverables:
- Fully functional OpenCart payment extension (.zip / OCMOD package).
- Documentation (setup, configuration, and developer notes).
- Source code with proper comments.
- Testing on sandbox and confirmation of successful transactions.

Skills Required:
- Strong experience in OpenCart module and payment gateway development.
- Proficient in PHP, MVC, OCMOD, and API integration.
- Familiar with OpenCart 3.x and 4.x structures.
- Understanding of webhooks, secure API handling, and payment workflows.

Note: We prefer a developer who can ensure long-term support and maintenance for future updates and current budget is $50-100 Max.

Thank you.