WIP feat: support Kafka messages with nullable or empty partition key

[sergioamribeiro]

Description

This merge request adds protection for the kafka messages that arrive without a value for the partition key (null or empty). The Retry will receive the messages and put them in the same queue and follow that order to process

Fixes # (10)

How Has This Been Tested?

We've made some unit and integration tests (see EmptyPartitionKeyRetryDurableTests class)

Checklist

• [X] My code follows the style guidelines of this project
• [X] I have performed a self-review of my own code
• [X] I have added tests to cover my changes
• [ ] I have made corresponding changes to the documentation

Disclaimer

By sending us your contributions, you are agreeing that your contribution is made subject to the terms of our Contributor Ownership Statement