Machine Payments Protocol client (Stripe/Tempo).
Handles the HTTP 402 flow using the MPP challenge/credential scheme.
The server returns WWW-Authenticate: Payment with a challenge; this
module decodes it, signs a payment credential, and builds the
Authorization: Payment header for the retry request.
Header Flow
- Server ->
402+WWW-Authenticate: Payment <base64 challenge> - Client -> retry +
Authorization: Payment <base64 credential> - Server ->
200+Payment-Receipt: <base64 receipt>
Payment Methods
MPP supports multiple payment methods per challenge. This implementation handles EVM-based methods (Tempo, ETH, ERC-20). Stripe (fiat) methods are detected but not yet implemented.