Java 8 and Backport new PR

[grrolland]

Hi,

I just make a PR and you merge it, many thanks.

Unfornunately, I'm using vault-java-driver in AWS Glue Jobs (v4.0), but AWS only support runtime on jvm 1.8 (yes, my bad, I don't verify before). And as this libs is the only one in java (or scala) that is always supported, I have no other choice to ask that :

Do you think it will be possible to release a java 8 compatible version from the 5.4.0 tags and backporting the 6.0.0 to 6.2.0+ PR ?

I can do that, if you are right.

Regards

[grrolland]

I have a bakported version to java 8 here, if you like to see : https://github.com/grrolland/vault-java-driver/tree/backport_5.4.1