Fine tune Kafka Configurer Module

[smcvb]

At the moment, the only easy approach to configure the Kafka Extension in an Axon project, is to use the kafka-spring-boot-starter dependency provided.
It would be beneficial if the kafka module would contain a ConfigurerModule implementation, which for example could be tied in through the Service Loader mechanism, to configure Kafka outside of the scope of Spring (Boot) too.

[smcvb]

A ModuleConfiguration implementation for Kafka Message Sources has been introduced in #17, more specifically PR #24.

[smcvb]

This issue is paramount to move the Kafka Extension from Axon 4 to Axon 4.5, due to the graceful startup and shutdown process.
Being able to configure everything in one spot greatly simplifies that, hence why this issue's priority is increased.

[smcvb]

After some further investigation, a more trivial solution was spotted to make this work.
Furthermore, since Kafka's Producer and Consumer require an abundance of properties, it's not straightforward to derive a concise ModuleConfiguration for the Kafka Module that doesn't use Spring.
This adjusts the priority and usefulness quite some.