Apply modernizer-maven-plugin to build

modernizer-maven-plugin can catch outdated Java coding paradigms that have been superseded by newer Java language features.

Applying the recommended changes from this plugin can help a project avoid breakages, incompatibilities, and changes in behavior, across Java versions. It can also help reduce dependencies by suggesting changes that leverage built-in Java classes rather than commonly-used external libraries that were written to add convenient features before those features were added to Java itself.

Adding the plugin to the build is simple, but working through all the items it catches is tedious. I've already begun this work.