Java 8 is end of support, time to move to decent java versions

[sebastienvermeille]

As maintainer doing this in my free time,
I strongly consider removing support of old versions of Java and benefit from new language features.
The same issue also occurs with the protoc protobuf versions used (they are not even available as download from github actions anymore (so old...)

The next release will probably be a major one including :

• full upgrade to JDK to 20
• full upgrade to latests protoc/protobuf versions
• full upgrade to latest maven version
• introduction of unit tests framework (easier and faster to test portion of code rather than the integrations tests already in place)

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I leave this ticket open to give a bit time to think about it and listen to the community voice too if you have any reason to not upgrade etc.

A support for a very legacy java version (i.e. java 8) could be discussed and deployed if sponsored eventually. (As only companies are dealing with so outdated java version anyway I believe it's fair)

What do you think ?