[FEATURE] Add an integration test that runs on JDK8

[dblock]

Is your feature request related to a problem?

Coming here via #156, in #767 we restored support for JDK8, but did not enable CI.

What solution would you like?

A workflow that exercises the client on JDK8. It could mean building on 11, but executing an integration test on a version 8 runtime.

What alternatives have you considered?

Let JDK8 support fail without notice.

Do you have any additional context?

#156 (comment)

[reta]

Thanks @dblock , I will take it, have some ideas on how we could approach that