Testing: convenience method to make default instances.

This will facilitate those tests needing a merchant
backend, since it is currently not possible to make
instances without having first a default instance defined.

packages/taler-wallet-cli/src/integrationtests/harness.ts

@@ -1489,6 +1489,17 @@ export class MerchantService implements MerchantServiceInterface {
     config.write(this.configFilename);
   }
 
+  async addDefaultInstance(): Promise<void> {
+    return await this.addInstance({
+      id: "default",
+      name: "Default Instance",
+      paytoUris: [`payto://x-taler-bank/merchant-default`],
+      auth: {
+        method: "external",
+      },
+    });
+  }
+
   async addInstance(
     instanceConfig: PartialMerchantInstanceConfig,
   ): Promise<void> {

packages/taler-wallet-cli/src/integrationtests/test-bank-api.ts

@@ -81,7 +81,7 @@ export async function runBankApiTest(t: GlobalTestState) {
 
   await merchant.start();
   await merchant.pingUntilAvailable();
-
+  await merchant.addDefaultInstance();
   await merchant.addInstance({
     id: "minst1",
     name: "minst1",