Cleanup integration tests

[turing85]

• When no message can be received, return null
• Where possible, rely on RestAssured

[github-actions]

🚦Reports for run #777🚦

Reports will be posted here as they get available.

🥳 JUnit JVM Test passed

Passed	Failed	Skipped
✅ 170	❌ 0	⚠️ 0

You can see the report here.

🥳 JUnit Native Test passed

Passed	Failed	Skipped
✅ 109	❌ 0	⚠️ 0

You can see the report here.

[middagj]

What is up with the formatter?

[turing85]

What is up with the formatter?

Do you mean the // @formatter:off? If you take it out, the formatter is of the oppinion that all of this should go on one line. Or on two, with random line breaks. Not really readable. I find that the test flow is much more readable with those line breaks