Add impsort-maven-plugin to ensure Java imports are well sorted.

[sbernard31]

impsort-maven-plugin allow to check if Java import are sorted correctly using :

mvn impsort:check

Java import can be sorted with :

mvn impsort:sort

This validation will be automatically done during build, when mvn clean install is called.

About wildcard(*), to have consistent import, I decide to forbid it using checkstyle rules.

All those will be automatically check on new PR using github actions. Errors will be reported like that : sbernard31#13