Fee calculation is wrong

[dvc94ch]

So the preprocess request takes the utxo input operations, but not the outputs. Then it estimates the size and returns it as options to be passed to the metadata endpoint. The metadata endpoint then calculates a fee, which is too low, since the estimated size doesn't account for the outputs. Then the payloads takes the inputs and outputs where the first output is the amount to send and the second output is sum(inputs) - amount_to_send - suggested_fee, resulting in the transaction getting rejected.

[dvc94ch]

looks like I missread the code:

// ConstructionPreprocess implements the /construction/preprocess
// endpoint.
func (s *ConstructionAPIService) ConstructionPreprocess(
    ctx context.Context,
    request *types.ConstructionPreprocessRequest,
) (*types.ConstructionPreprocessResponse, *types.Error) {
    descriptions := &parser.Descriptions{
        OperationDescriptions: []*parser.OperationDescription{
            {
                Type: bitcoin.InputOpType,
                Account: &parser.AccountDescription{
                    Exists: true,
                },
                Amount: &parser.AmountDescription{
                    Exists:   true,
                    Sign:     parser.NegativeAmountSign,
                    Currency: s.config.Currency,
                },
                CoinAction:   types.CoinSpent,
                AllowRepeats: true,
            },
        },
    }

    matches, err := parser.MatchOperations(descriptions, request.Operations)
    if err != nil {
        return nil, wrapErr(ErrUnclearIntent, err)
    }

this actually ignores outputs, doesn't reject them