[Async] [Kafka endpoint] Publish to a topic

[mouligno]

🌈 Feature

As an Async API Publisher, I want to publish to a specific topic using the Kafka connector.

🌄 Additional information

• Create a producer
• push message to specific topic
• Authentification is out of scope
• New endpoint plugin

Example of initialization -
https://github.com/gravitee-io/gravitee-poc-sme/blob/master/src/main/java/io/gravitee/poc/sme/gateway/connector/endpoint/async/impl/KafkaEndpointAsyncConnector.java

🦸 Acceptance criteria

• Given an async API with a kafka topic as endpoint
• Then I can publish a new record to my topic through my API

[guillaumelamirand]

Two PR are opened :

1. feat(kafka): add kafka endpoint gravitee-api-management#2379
2. feat(kafka): add kafka endpoint gravitee-gateway-api#137

In order to test you will need to use http post entrypoint which is under development

[LiliaEn]

Tested locally using 3.19.0 version.
The following scenarios were covered:

• Create an API with http-post entrypoint and kafka endpoint and a topic
• Create a plan+ publish and start the API
• Send a post request with a message and check on the Kafka Client UI that the message is displayed on the appropriate topic