Fix callback signature mismatch and add new payment methods (DANA & OTHERBANKVA)

[justpiple]

Summary

This pull request fixes an issue with callback signature verification and adds new payment methods to the payment module.

Bug Fix

• Updated the callback signature generation to use JSON.stringify(body) instead of body.toString().
• This change resolves a signature mismatch caused by toString() returning "[object Object]" when applied to an object.

Payment Methods Update

• Added support for the DANA and OTHERBANKVA payment methods.
• Updated the isPaymentMethod helper and PaymentMethod type to include the new methods.