* Verify maven dependency checksums
Maven build process will compute checksums for our dependencies and verify them against a local "trusted checksums" file, and fail the build if they do not match. This process is local and independent of checksums stored and downloaded from maven repositories.
SNAPSHOT dependencies are not verified (but released versions should never depend on SNAPSHOT dependencies).
* Update kamon and kanela-agent
Previous version was not compatible with JDK21, see https://github.com/kamon-io/kanela/issues/150.
* Add and configure maven wrapper to use maven 3.9.9
This will make it easier to control which version of maven is used to build eclair, which in turns makes deterministic builds easier, as well as using recent compiler options (to target newer JDKs for example).
For example, even recent versions of Github runner images use an old version of maven and there is no easy way to upgrade.
* Update Dockerfile
We now use multiarch (amd64/arm64) base images.
* Run CI tests with JDK21
* Update doc to recommend Adoptium OpenJDK21
* Target Java 21
Eclair now targets Java 21 and will require a compatible Java Runtime Environment.
It will no longer work on JRE 11 and JRE 17.
