feat(deps): Bump Micronaut platform to 5.0.0 (GA)

[jamesfredley]

Draft - stacked on top of apache#15675. This PR uses the Spring Boot 4.0.6 branch (deps/spring-boot-4.0.6) as its base so the dependency-version fallout from that bump does not muddy this one.

Bumps micronautPlatformVersion from 5.0.0-M2 to 5.0.0 (GA, published to Maven Central on 2026-05-20).

Release notes / changelog: https://github.com/micronaut-projects/micronaut-platform/releases/tag/v5.0.0
Maven Central: https://repo1.maven.org/maven2/io/micronaut/platform/micronaut-platform/5.0.0/

What's in this first commit

The minimum change set that keeps validateDependencyVersions green after the bump:

• gradle.properties: micronautPlatformVersion=5.0.0-M2 -> 5.0.0.
• dependencies.gradle: bump the grails-micronaut-bom Groovy override from 5.0.5 to 5.0.6 so our strict pin matches Micronaut 5 GA's managed groovy.version. Spock stays at 2.4-groovy-5.0 (unchanged in GA).
• grails-bom/micronaut/build.gradle: refresh the comment on the tools.jackson exclude. Micronaut 5.0.0 ships jackson-bom 3.1.3 while Spring Boot 4.0.6 ships 3.1.2 - the platforms still disagree on the patch, just in the opposite direction now. The exclude itself stays in place so spring-boot-dependencies remains the single source of truth for Jackson 3.

Notable upstream version moves (5.0.0-M2 -> 5.0.0)

Read directly from the published micronaut-platform-5.0.0.pom:

Property	M2	5.0.0 GA
micronaut.core.version	5.0.0-M23	5.0.0
micronaut.data.version	5.0.0-M5	5.0.1
micronaut.serde.version	3.0.0-M7	3.0.0
micronaut.mongo.version / micronaut.mongodb.version	6.0.1-M1	6.0.1
micronaut.langchain4j.version	2.0.0-M1	2.0.0
jackson.version	3.1.0	3.1.3
groovy.version	5.0.4	5.0.6
spock.version	2.4-groovy-5.0	2.4-groovy-5.0
spring.boot.version	4.0.3	4.0.6 (matches our pin)
spring.version	7.0.6	7.0.7

Known platform-level breaking changes

From the v5.0.0 release notes - flagged here so reviewers know what to watch for in subsequent commits:

• RxJava 2 removed from BOM. io.reactivex:rxjava and io.micronaut.rxjava2:* are no longer managed by the platform. Our micronautRxjava2Version=2.9.0 in gradle.properties is already floated outside the BOM (comment: "micronaut libraries not in the bom due to the potential for spring mismatches"), so the existing pin still works - but consumers should be aware.
• MicroStream removed from BOM. Replaced by EclipseStore (micronaut.eclipsestore.version=2.0.0).
• jaxrs.api.version 3.1.0 -> 4.0.0 (Jakarta RESTful Web Services 4).
• kafka.version 3.9.1 -> 4.2.0 - major Kafka client jump.

None of these affect anything grails-core currently consumes, but they are landmines for downstream Grails-on-Micronaut apps.

What is NOT addressed yet

This PR intentionally ships the minimum-viable bump first. Expect follow-up commits for:

• Any compile/test fallout in grails-micronaut, grails-test-examples/micronaut*, and grails-test-examples/plugins/micronaut-singleton.
• Possible Serde alignment: micronautSerdeJacksonVersion=2.11.0 in gradle.properties is still on the Micronaut Serde 2.x line while Micronaut 5 GA ships Serde 3.0.0. It is intentionally floated outside the BOM today; whether to bump it is a separate decision pending what the graphql test examples actually need.
• micronautRxjava2Version=2.9.0 - same situation; out-of-band pin, likely fine but worth confirming.
• grails-forge stays on micronautVersion=4.10.10 (the Forge IS a Micronaut 4.x app, per the comment at grails-forge/gradle.properties:27). Out of scope for this PR.

Verification so far:

./gradlew validateDependencyVersions          # root: BUILD SUCCESSFUL
./gradlew :grails-gradle:validateDependencyVersions  # grails-gradle: BUILD SUCCESSFUL

Full build / test execution is the next step and likely the source of most of the remaining work on this branch.

[jamesfredley]

Superseded by apache#15677 (same commits, apache-hosted branches, stacked on apache#15676).