refactor(sdk-coin-apt): check feePayerAddress for signablePayload

TICKET: COIN-2838

Author: bhavidhingra

modules/sdk-coin-apt/src/lib/transaction/transaction.ts

@@ -16,9 +16,13 @@ import {
   DEFAULT_MAX_GAS_AMOUNT,
   Ed25519PublicKey,
   Ed25519Signature,
+  FeePayerRawTransaction,
+  generateSigningMessage,
   generateUserTransactionHash,
   Hex,
   Network,
+  RAW_TRANSACTION_SALT,
+  RAW_TRANSACTION_WITH_DATA_SALT,
   RawTransaction,
   SignedTransaction,
   SimpleTransaction,
@@ -286,6 +290,23 @@ export abstract class Transaction extends BaseTransaction {
     return new BigNumber(this.gasUsed).multipliedBy(this.gasUnitPrice).toString();
   }
 
+  public get signablePayload(): Buffer {
+    return this.feePayerAddress ? this.getSignablePayloadWithFeePayer() : this.getSignablePayloadWithoutFeePayer();
+  }
+
+  private getSignablePayloadWithFeePayer(): Buffer {
+    const feePayerRawTxn = new FeePayerRawTransaction(
+      this._rawTransaction,
+      [],
+      AccountAddress.fromString(this._feePayerAddress)
+    );
+    return Buffer.from(generateSigningMessage(feePayerRawTxn.bcsToBytes(), RAW_TRANSACTION_WITH_DATA_SALT));
+  }
+
+  private getSignablePayloadWithoutFeePayer(): Buffer {
+    return Buffer.from(generateSigningMessage(this._rawTransaction.bcsToBytes(), RAW_TRANSACTION_SALT));
+  }
+
   private generateTxnId() {
     if (
       !this._senderSignature ||

modules/sdk-coin-apt/src/lib/transaction/transferTransaction.ts

@@ -1,28 +1,13 @@
 import { Transaction } from './transaction';
 import { AptTransactionExplanation, TransferTxData } from '../iface';
 import { TransactionRecipient, TransactionType } from '@bitgo/sdk-core';
-import {
-  AccountAddress,
-  FeePayerRawTransaction,
-  generateSigningMessage,
-  RAW_TRANSACTION_WITH_DATA_SALT,
-} from '@aptos-labs/ts-sdk';
 
 export class TransferTransaction extends Transaction {
   constructor(coinConfig) {
     super(coinConfig);
     this._type = TransactionType.Send;
   }
 
-  public get signablePayload(): Buffer {
-    const feePayerRawTxn = new FeePayerRawTransaction(
-      this._rawTransaction,
-      [],
-      AccountAddress.fromString(this._feePayerAddress)
-    );
-    return Buffer.from(generateSigningMessage(feePayerRawTxn.bcsToBytes(), RAW_TRANSACTION_WITH_DATA_SALT));
-  }
-
   /** @inheritDoc */
   explainTransaction(): AptTransactionExplanation {
     const displayOrder = [