update Fee calculation

[piadascripto]

• [ ] Add the fee amount to the payment transaction instead of subtracting it from the amount to be paid.
• [ ] Remove TOTAL_FEE and leave a parameter for Kyodo and another for Community

[piadascripto]

@nomadbitcoin what to you think to add a option here to either the beneficiary or the payer to be in charge of the fee? That way we can offer this option and be more flexible

[piadascripto]

@nomadbitcoin the way I see now is that payers should bear the fee when they pay. Beneficiary should bear the fee when they want to do bridges, swaps and withdrawals.