wallet: remove PSBT legacy credit helper

Remove the PSBT legacy credit helper after every PSBT credit and
parent lookup has moved to the store-backed path.

Author: yyforyongyu

wallet/psbt_manager.go

@@ -21,7 +21,6 @@ import (
 	"github.com/btcsuite/btcwallet/waddrmgr"
 	"github.com/btcsuite/btcwallet/wallet/internal/db"
 	"github.com/btcsuite/btcwallet/wallet/txauthor"
-	"github.com/btcsuite/btcwallet/wtxmgr"
 )
 
 var (
@@ -568,20 +567,6 @@ func validatePsbtParentOutput(outPoint wire.OutPoint,
 	return utxo, nil
 }
 
-// findCredit determines whether a transaction's details contain a credit for a
-// specific output index.
-func findCredit(txDetail *wtxmgr.TxDetails,
-	outputIndex uint32) *wtxmgr.CreditRecord {
-
-	for i := range txDetail.Credits {
-		if txDetail.Credits[i].Index == outputIndex {
-			return &txDetail.Credits[i]
-		}
-	}
-
-	return nil
-}
-
 // FundPsbt performs coin selection and funds the PSBT.
 //
 // It executes the funding logic by:

wallet/psbt_manager_test.go

@@ -24,7 +24,6 @@ import (
 	"github.com/btcsuite/btcwallet/waddrmgr"
 	"github.com/btcsuite/btcwallet/wallet/internal/db"
 	"github.com/btcsuite/btcwallet/wallet/txauthor"
-	"github.com/btcsuite/btcwallet/wtxmgr"
 	"github.com/stretchr/testify/mock"
 	"github.com/stretchr/testify/require"
 )
@@ -56,67 +55,6 @@ func testStoreUtxoInfo(outPoint wire.OutPoint,
 	}
 }
 
-// TestFindCredit tests that the findCredit helper returns true if a credit
-// exists at the specified index, and false otherwise.
-func TestFindCredit(t *testing.T) {
-	t.Parallel()
-
-	// Arrange: Create TxDetails with credits at indices 0 and 2.
-	txDetails := &wtxmgr.TxDetails{
-		Credits: []wtxmgr.CreditRecord{
-			{Index: 0},
-			{Index: 2},
-		},
-	}
-
-	// Arrange: Define test cases to check for credits at various indices.
-	testCases := []struct {
-		name          string
-		index         uint32
-		expectedFound bool
-	}{
-		{
-			name:          "credit exists at index 0",
-			index:         0,
-			expectedFound: true,
-		},
-		{
-			name:          "credit exists at index 2",
-			index:         2,
-			expectedFound: true,
-		},
-		{
-			name:          "credit does not exist at index 1",
-			index:         1,
-			expectedFound: false,
-		},
-		{
-			name:          "credit does not exist at index 3",
-			index:         3,
-			expectedFound: false,
-		},
-	}
-
-	for _, tc := range testCases {
-		t.Run(tc.name, func(t *testing.T) {
-			t.Parallel()
-
-			// Act: Call findCredit with the configured TxDetails
-			// and index.
-			cred := findCredit(txDetails, tc.index)
-
-			// Assert: Verify that the returned credit record
-			// matches the expected outcome.
-			if tc.expectedFound {
-				require.NotNil(t, cred)
-				require.Equal(t, tc.index, cred.Index)
-			} else {
-				require.Nil(t, cred)
-			}
-		})
-	}
-}
-
 // TestFetchAndValidateUtxoSuccess tests that fetchAndValidateUtxo correctly
 // retrieves wallet-owned UTXO and transaction details.
 func TestFetchAndValidateUtxoSuccess(t *testing.T) {