fix(kotlin-spring): use Jackson 3 annotation package in model imports

[yonatankarp]

Summary

• Fixes importMapping in KotlinSpringServerCodegen to derive Jackson annotation package from useJackson3 flag instead of hardcoding com.fasterxml.jackson
• Adds missing tools.jackson.core:jackson-annotations dependency to all Spring Boot 4 build templates (Gradle + Maven) for spring-boot, spring-cloud, and spring-declarative-http-interface libraries
• Fixes hardcoded com.fasterxml.jackson.dataformat.yaml.YAMLMapper import in homeController.mustache to use {{jacksonPackage}}
• Adds test verifying generated model files use tools.jackson.annotation when Jackson 3 is enabled
• Regenerates kotlin-springboot-4 sample with corrected imports and dependencies

Bug

When using useSpringBoot4: true / useJackson3: true with the kotlin-spring generator:

1. Generated model source files imported com.fasterxml.jackson.annotation.* (Jackson 2) instead of tools.jackson.annotation.* (Jackson 3)
2. Build files were missing the tools.jackson.core:jackson-annotations dependency, causing compile failures even after fixing the imports

---

Summary by cubic

Fix Kotlin Spring generation for Jackson 3 on Spring Boot 4: keep model annotations in com.fasterxml.jackson.annotation, use {{jacksonPackage}} for YAMLMapper, and pin Jackson 3 dataformat/module versions. Tests and Spring Boot 4 samples updated.

• Bug Fixes

  • KotlinSpringServerCodegen: always import JsonProperty/JsonCreator/JsonValue from com.fasterxml.jackson.annotation (annotations did not move in Jackson 3).
  • homeController.mustache: import {{jacksonPackage}}.dataformat.yaml.YAMLMapper.

• Dependencies

  • Spring Boot 4 templates: set 3.1.0 for tools.jackson.dataformat:jackson-dataformat-yaml, tools.jackson.dataformat:jackson-dataformat-xml, and tools.jackson.module:jackson-module-kotlin via val jackson3Version / <jackson3.version>.
  • Do not add tools.jackson.core:jackson-annotations.

^{Written for commit 9e9bff4. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 11 files

[Picazsoo]

If you added a test, it would be good to revert the implementation (leave the test intact), push, let the test fail and the again restore the fix and push and let the test pass. That way it is somewhat proven that the test passes because it tests for the issue.
You can think of it like a fake TDD.

[yonatankarp]

@Picazsoo it was done like that, I squashed them before I asked for a review, but next time I'm happy to keep the commits separated 😄

[Picazsoo]

Sorry, that did not occur to me