Switch code style to Google's Java Code Style

[koppor]

I am so fed up that

• contributors are not able to configure IntelliJ properly (e.g., [WIP] This relativizes the PDF's filepaths after importing through "Find Unlinked Files" JabRef/jabref#10582). We tried OpenRewrite for auto fixing, but did not work.
• our reformatting broke a few months ago for exceptions (e.g., Display files from referenced crossref in entry table (Toro520 version) JabRef/jabref#10577 (review))

Thus, I am looking for good autoformatting tools. The most prominent tool with style guide is Google's:

• Google's Java Code Style (in the AOSP variant) provides a nice formatting.
• Google's Java Format toolchain provides auto format. See https://github.com/axel-op/googlejavaformat-action#google-java-format-action

This PR adds it.

Let's hope for the best that the reformatting action a) really adds a new commit and b) the contributors will be able to pull these changes 😅🙈

I am aware, that there is no maintained gradle plugin.

I am also aware, that Eclipse AOSP since 5 years (google/google-java-format#251), but maybe, this will be resolved.

---

Blockers

• Unexpectedly change the AST google/google-java-format#980

Mandatory checks

• Change in CHANGELOG.md described in a way that is understandable for the average user (if applicable)
• Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (for UI changes)
• Checked developer's documentation: Is the information available and up to date? If not, I outlined it in this pull request.
• Checked documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request to the documentation repository.

[github-actions]

Your code currently does not meet JabRef's code guidelines. We use Checkstyle to identify issues. The tool reviewdog already placed comments on GitHub to indicate the places. See the tab "Files" in you PR. Please carefully follow the setup guide for the codestyle. Afterwards, please run checkstyle locally and fix the issues.

More information on code quality in JabRef is available at https://devdocs.jabref.org/getting-into-the-code/development-strategy.html.

[Siedlerchr]

Mabye spotless ? https://github.com/diffplug/spotless

[koppor]

• spotless has issues with Gradle 8: Bug: Spotless gradle plugin execution fails with Gradle 8.0 diffplug/spotless#1572 (comment)
• spotless fails if code style is not met -- linting support is future work: Add support for linters diffplug/spotless#1097

Wait for another PR - I have success with palantir-java-format.

That is a) more maintained and b) seems to work well and c) has better formatting than GJF:

(1) google-java-format output:

private static void configureResolvedVersionsWithVersionMapping(Project project) {
    project.getPluginManager()
            .withPlugin(
                    "maven-publish",
                    plugin -> {
                        project.getExtensions()
                                .getByType(PublishingExtension.class)
                                .getPublications()
                                .withType(MavenPublication.class)
                                .configureEach(
                                        publication ->
                                                publication.versionMapping(
                                                        mapping -> {
                                                            mapping.allVariants(
                                                                    VariantVersionMappingStrategy
                                                                            ::fromResolutionResult);
                                                        }));
                    });
}

(1) palantir-java-format output:

private static void configureResolvedVersionsWithVersionMapping(Project project) {
    project.getPluginManager().withPlugin("maven-publish", plugin -> {
        project.getExtensions()
                .getByType(PublishingExtension.class)
                .getPublications()
                .withType(MavenPublication.class)
                .configureEach(publication -> publication.versionMapping(mapping -> {
                    mapping.allVariants(VariantVersionMappingStrategy::fromResolutionResult);
                }));
    });
}

[koppor]

New try at #663