feat: Lightning Network Integration

[AbdelStark]

Lightning Network Integration for Gakimint

Description

Currently, Gakimint uses a simulated Lightning Network, and all payments for mint quotes are automatically considered as being made. We need to integrate a real Lightning Network implementation to handle actual payments.

Objectives

1. Replace the mock Lightning Network service with a real Lightning Network implementation.
2. Implement proper payment verification for mint quotes.
3. Update the mint quote workflow to handle real Lightning Network payments.

Tasks

• Research and choose a suitable Lightning Network library or implementation for Elixir.
• Implement a new LightningNetworkService module to interface with the chosen Lightning Network implementation.
• Update the create_invoice function to generate real Lightning invoices.
• Implement a proper check_payment function that verifies the payment status with the Lightning Network.
• Update the MintController to use the new LightningNetworkService instead of the mock version.
• Modify the create_mint_quote and get_mint_quote functions to handle real payment states.
• Implement error handling for failed or expired Lightning payments.
• Update tests to work with the new Lightning Network integration.
• Add configuration options for connecting to a Lightning Network node.
• Document the setup process for connecting Gakimint to a Lightning Network node.

Additional Considerations

• Security: Ensure that the Lightning Network integration follows best practices for handling payments securely.
• Performance: Consider the impact of real-time payment verification on the system's performance.
• Error Handling: Implement robust error handling for various Lightning Network-related scenarios (e.g., network issues, payment failures).
• Testnet Support: Consider adding support for both mainnet and testnet Lightning Network operations.

Resources

• NUT-04
• LNbits
• River bitcoinex Elixir library

Definition of Done

• Gakimint can create real Lightning invoices for mint quotes.
• Payments for mint quotes are verified against actual Lightning Network transactions.
• The system correctly handles different payment states (unpaid, paid, expired).
• All tests pass with the new Lightning Network integration.
• Documentation is updated to reflect the new Lightning Network setup and configuration.

Estimated Effort

Medium to High: This is a significant change that affects core functionality and requires integration with external systems.

Priority

High: This is a critical feature for the real-world usage of Gakimint.