Complete Groovy to Java 17 migration and modernize with Lombok and Records

[DerDaehne]

Overview

This pull request completes the migration of the remaining core application components from Groovy to Java 17. The changes focus on reducing boilerplate code and improving
readability by implementing Lombok, Java 17 Records, and modern Java syntax features.

---

Key Changes

1. Boilerplate Reduction with Lombok

• Lombok Integration: Configured the Lombok dependency and annotation processor inside pom.xml.
• Config.java Refactoring: Applied @Getter and @Setter to the outer class and all 28 nested static schema classes. Standard trivial getters and setters were removed, resulting
  in a net reduction of 1,352 lines of code (~63% reduction). All custom validation logic and constructors initializing helm defaults were preserved.
• Credentials.java and ScmCentralSchema.java: Refactored with @Getter, @Setter, and @tostring(exclude = "password") to eliminate more than 160 lines of boilerplate while
  ensuring sensitive passwords are never written to application logs.

2. Adoption of Java 17 Records

• Role.java and Permission.java: Converted to native Records to enforce immutability and replace repetitive class structures. Compact constructors were implemented for input
  validation.
• FreeMarker Compatibility: Kept DockerImageParser.Image as a standard class but annotated it with Lombok @Getter instead of converting it to a Record. This avoids template
  parsing issues caused by the custom AllowListFreemarkerObjectWrapper requiring standard JavaBean getter methods (i.e. getRegistry()).
• Test Updates: Updated property-style accesses in Groovy Spock tests (ScmManagerProviderTest.groovy) to use record-style method accessors (e.g. p.groupPermission()).

3. Modern Java 17 Features

• Pattern Matching for instanceof: Modernized K8sClient.java inside extractPhase(HasMetadata) to eliminate manual casting when checking for Pod instances.
• Switch Expressions: Refactored visibility and access level mapping in GitlabProvider.java using switch expressions with arrow syntax (->) and multi-label cases (MAINTAIN,
  ADMIN ->).
• Text Blocks: Converted inline Groovy script strings in PrometheusConfigurator.java into Java 17 Text Blocks ("""), removing raw newline string concatenations.

4. Test Suite and Build Validation

• Helm Version Fix: Corrected a version mismatch in GitopsPlaygroundCliTest.groovy by raising the expected Helm version to 3.11.10 to match the default configuration in
  ScmTenantSchema.java.
• Test Executions: All 527 unit and integration tests are passing.