feat(sdk-coin-iota): updating explain transaction

modules/sdk-coin-iota/src/iota.ts

@@ -166,13 +166,22 @@ export class Iota extends BaseCoin {
       fee = new BigNumber(transactionExplanation.fee.fee);
     }
 
-    // assume 1 sender, who is also the fee payer
+    const outputAmount = transactionExplanation.sponsor
+      ? new BigNumber(transactionExplanation.outputAmount).toFixed()
+      : new BigNumber(transactionExplanation.outputAmount).plus(fee).toFixed(); // assume 1 sender, who is also the fee payer
+
     const inputs = [
       {
         address: senderAddress,
-        amount: new BigNumber(transactionExplanation.outputAmount).plus(fee).toFixed(),
+        amount: outputAmount,
       },
     ];
+    if (transactionExplanation.sponsor) {
+      inputs.push({
+        address: transactionExplanation.sponsor,
+        amount: fee.toFixed(),
+      });
+    }
 
     const outputs: {
       address: string;

modules/sdk-coin-iota/src/lib/iface.ts

@@ -8,6 +8,8 @@ import {
 
 export interface TransactionExplanation extends BaseTransactionExplanation {
   type: BitGoTransactionType;
+  sender: string;
+  sponsor?: string;
 }
 
 export type TransactionObjectInput = {

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

@@ -229,6 +229,8 @@ export abstract class Transaction extends BaseTransaction {
       changeOutputs: [],
       changeAmount: '0',
       fee: { fee: this.gasBudget ? this.gasBudget.toString() : '' },
+      sender: this.sender,
+      sponsor: this.gasSponsor,
       type: this.type,
     };