feat(abstract-utxo): make pubs parameter required for custom signing function

Ensure pubs parameter is always required when using custom signing functions
to maintain consistency and prevent errors. Update function signature in
the interface and implementation to reflect this requirement.

Issue: BTC-3018

Co-authored-by: llm-git <llm-git@ttll.de>

Author: OttoAllmendinger

modules/abstract-utxo/src/abstractUtxoCoin.ts

@@ -801,13 +801,13 @@ export abstract class AbstractUtxoCoin
   /**
    * Sign a transaction with a custom signing function. Example use case is express external signer
    * @param customSigningFunction custom signing function that returns a single signed transaction
-   * @param signTransactionParams parameters for custom signing function. Includes txPrebuild and pubs (for legacy tx only).
+   * @param signTransactionParams parameters for custom signing function. Includes txPrebuild and pubs
    *
    * @returns signed transaction as hex string
    */
   async signWithCustomSigningFunction<TNumber extends number | bigint>(
     customSigningFunction: UtxoCustomSigningFunction<TNumber>,
-    signTransactionParams: { txPrebuild: TransactionPrebuild<TNumber>; pubs?: string[] }
+    signTransactionParams: { txPrebuild: TransactionPrebuild<TNumber>; pubs: string[] }
   ): Promise<SignedTransaction> {
     const txHex = signTransactionParams.txPrebuild.txHex;
     assert(txHex, 'missing txHex parameter');

modules/sdk-core/src/bitgo/baseCoin/iBaseCoin.ts

@@ -613,7 +613,7 @@ export interface IBaseCoin {
   presignTransaction(params: PresignTransactionOptions): Promise<PresignTransactionOptions>;
   signWithCustomSigningFunction?(
     customSigningFunction: CustomSigningFunction,
-    signTransactionParams: { txPrebuild: TransactionPrebuild; pubs?: string[] }
+    signTransactionParams: { txPrebuild: TransactionPrebuild; pubs: string[] }
   ): Promise<SignedTransaction>;
   newWalletObject(walletParams: any): IWallet;
   feeEstimate(params: FeeEstimateOptions): Promise<any>;

modules/sdk-core/src/bitgo/wallet/wallet.ts

@@ -2194,7 +2194,11 @@ export class Wallet implements IWallet {
 
     if (_.isFunction(params.customSigningFunction)) {
       if (typeof this.baseCoin.signWithCustomSigningFunction === 'function') {
-        return this.baseCoin.signWithCustomSigningFunction(params.customSigningFunction, signTransactionParams);
+        assert(pubs, 'pubs are required for custom signing');
+        return this.baseCoin.signWithCustomSigningFunction(params.customSigningFunction, {
+          ...signTransactionParams,
+          pubs,
+        });
       }
       const keys = await this.baseCoin.keychains().getKeysForSigning({ wallet: this });
       const signTransactionParamsWithSeed = {