* Don't use default interface method bytecode optimization for target 1.8
* Update fix to rely on jvm-default=enable/@JvmDefault in order to preserve java compatibility:
* Integrate Spotless in build
* Update CONTRIBUTING.md
* Move improperly placed copyright comments
* Update copyright indent
* Don't format test fixtures
* Run spotlessApply over the whole repo
* Remove checkstyle configs
* Run spotlessCheck on CI