debezium/dbz#1470 Fix JWTAuthenticatorTest + slight refactor

[MV-GH]

Fixes debezium/dbz#1470

Initial I thought I had broken JWTAuthenticatorTest with my PR but it failed already before that.

I fixed the tests, and did some slight refactors.

Before the refreshEndpoint called the "authenticate" endpoint instead. (it used the authRequestBuilder iso refreshRequestBuilder

The public API has slightly changed with authenticate but I assume there is no requirement to keep it backwards compatible.

Also in recordSent IOException is wrapped into a interrupt? There is test for this. So I have kept it. But imo this doesn't make sense. IOException should just be failure. (connection broke) so that the retry system can catch this. Iso propagating up as an interrupt.

The HttpIT tests still don't work. But i'll probably fix those too. Then I am probably going to add better concurrency options to this sink bc the current setup; Is a sequential blocking implementation. And If you have 5ms time per request you can only send at 200/s.

Also, where can you see the "hash" of the nightly build. I tried with nightly of yesterday but I could still repro the issue.

[jpechane]

@MV-GH Good job! COuld you please try to make sure that your PR contains all the changes from #237 so I could close mine?

[MV-GH]

@jpechane I have included all the changes from #237

Could you answer the IOException stuff I mentioned?

[jpechane]

@MV-GH Yes, it makes sense to change the exception handling