[core] add IDE agnostic configuration

[Pankraz76]

Addressing the comment and issue of people use a lot of editors and very different versions, which is a valid concern—one good approach to handling this is using Spotless.

Applying a strictly enforced style can be challenging without a universal solution. Spot provides a way to apply the config out of the box, making it easier to maintain consistency.

• Replace checkstyle with Spotless & Google Java Style projectnessie/nessie#624

Intellij config

This is very specific but understandable, assuming we all use IDEA.

Its all there, we just need to use is.

• https://plugins.jetbrains.com/plugin/13180-palantir-java-format
• https://github.com/palantir/palantir-java-format

[Pankraz76]

example: #5635

[adangel]

Thanks for the suggestion. I think, it makes sense to add this config. But we need to mention it in the documentation, as not all IDEs/Editors use it by default. Some (like VS Code) need a plugin. So the relevant documentation needs to be updated:

• https://docs.pmd-code.org/latest/pmd_devdocs_building_intellij.html
• https://docs.pmd-code.org/latest/pmd_devdocs_building_eclipse.html
• https://docs.pmd-code.org/latest/pmd_devdocs_building_vscode.html
• https://docs.pmd-code.org/latest/pmd_devdocs_building_netbeans.html

Also, if we have this config, then I assume, we don't need e.g. the IntelliJ Specific config anymore?
-> https://docs.pmd-code.org/latest/pmd_devdocs_building_intellij.html#formatter-and-inspection-configuration / https://github.com/pmd/build-tools/tree/main/intellij-idea

[Pankraz76]

Also, if we have this config, then I assume, we don't need e.g. the IntelliJ Specific config anymore?
-> https://docs.pmd-code.org/latest/pmd_devdocs_building_intellij.html#formatter-and-inspection-configuration / https://github.com/pmd/build-tools/tree/main/intellij-idea

Yes I think so too, but @romani has different opinion. We will find out after migration, if we still need the file for manual config. @Anmol202005

ATM its configuration over convention, but actually we want the opposite approach convention over configuration.

The setting-up-checkstyle file is needed, as it will evolve into the new .editorconfig - as the keys are 1o1 the same, like discussed in: checkstyle/checkstyle#16349 (comment)