walletkit: add RPC GetTransaction

https://lightning.engineering/api-docs/api/lnd/wallet-kit/get-transaction/

The RPC is available since LND 0.18.0.

Author: starius

testdata/permissions.json

@@ -1136,6 +1136,14 @@
                 }
             ]
         },
+        "/walletrpc.WalletKit/GetTransaction": {
+            "permissions": [
+                {
+                    "entity": "onchain",
+                    "action": "read"
+                }
+            ]
+        },
         "/walletrpc.WalletKit/PendingSweeps": {
             "permissions": [
                 {

walletkit_client.go

@@ -101,6 +101,10 @@ type WalletKitClient interface {
 		addressType walletrpc.AddressType,
 		change bool) (btcutil.Address, error)
 
+	// GetTransaction returns details for a transaction found in the wallet.
+	GetTransaction(ctx context.Context,
+		txid chainhash.Hash) (Transaction, error)
+
 	PublishTransaction(ctx context.Context, tx *wire.MsgTx,
 		label string) error
 
@@ -481,6 +485,26 @@ func (m *walletKitClient) NextAddr(ctx context.Context, accountName string,
 	return addr, nil
 }
 
+// GetTransaction returns details for a transaction found in the wallet.
+func (m *walletKitClient) GetTransaction(ctx context.Context,
+	txid chainhash.Hash) (Transaction, error) {
+
+	rpcCtx, cancel := context.WithTimeout(ctx, m.timeout)
+	defer cancel()
+
+	rpcCtx = m.walletKitMac.WithMacaroonAuth(rpcCtx)
+
+	req := &walletrpc.GetTransactionRequest{
+		Txid: txid.String(),
+	}
+	resp, err := m.client.GetTransaction(rpcCtx, req)
+	if err != nil {
+		return Transaction{}, err
+	}
+
+	return unmarshallTransaction(resp)
+}
+
 func (m *walletKitClient) PublishTransaction(ctx context.Context,
 	tx *wire.MsgTx, label string) error {