FossBilling Payment Integration Extension

I need a developer to create an extension for FossBilling that integrates payment gateways, specifically PayPal and Stripe.

Key Requirements:
- Payment Integration: Add PayPal and Stripe as payment options.
- Additional Features (Optional): If possible, include features like recurring payments, refund processing, or transaction history.

Ideal Skills:
- Experience with FossBilling
- Proficiency in payment gateway integration
- Familiarity with PayPal and Stripe APIs
- Strong development skills in relevant programming languages (e.g., PHP, JavaScript)

Please provide examples of similar work done. Looking forward to your proposals!