SaveRequestKeyActivity.cs

[FunctionName(nameof(SaveRequestKeyActivity))]
public static async Task SaveRequestKeyActivity(
    [ActivityTrigger] DurableActivityContext context,
    [Table("KeySaveTable")] CloudTable table
    )
{
    var key = context.GetInput<string>();
    var insertOperation = TableOperation.Insert(new TableEntity(key, context.InstanceId));
    await table.ExecuteAsync(insertOperation);
}