EventHub output binding cannot send events from batch

[kevin808]

Please provide a succinct description of the issue.

Repro steps

Provide the steps required to reproduce the problem

1. Repo for reproduce: https://github.com/kevin808/functionapp-typescript-eventhubtrigger/tree/master
   It used a eventhub trigger to receive events and eventhub output binding to send events to another eventhub

import { AzureFunction, Context } from "@azure/functions"

const eventHubTrigger: AzureFunction = async function (context: Context, ingressEventHubMessagesConsumer: any[]): Promise<void> {
    ingressEventHubMessagesConsumer.forEach((message, index) => {
        context.log('eventHubTrigger Message received: ', message);
        context.bindings.egressEventHubMessageProducer = message;
        context.log('eventHubTrigger Message sent: ',index,message);
    });
};
 
export default eventHubTrigger;

2. Update the local.settings.json and EventHubTrigger/function.json accordingly.

3. Build and run the function app from local or deploy to Azure Function App.

4. Generate events in source eventhub

Expected behavior

When cardinality in EventHubTrigger/function.json set to many, all the events are sent to Event Hub.

Actual behavior

Only one event is sent to the Event Hub when a batch of events are received from Event Hub trigger even though the logs indicates all the events are sent.

Known workarounds

Set cardinality to one, all the events are sent successfully.