private Optional<ExternalContext> buildExternalContext(Config config) {
    /*
     * By default, use an empty ExternalContext here. In a custom fork of Samza, this can be implemented to pass
     * a non-empty ExternalContext. Only config should be used to build the external context. In the future, components
     * like the application descriptor may not be available.
     */
    return Optional.empty();
  }
Overrides of method should provide the following mandatory configurations
 1. bootstrap.servers
 2. key.deserializer
 3. value.deserializer
 4. auto.offset.reset
 5. group.id

@return {@link Properties} for the test kafka consumer
samza-test/src/test/java/org/apache/samza/test/harness/IntegrationTestHarness.java