Add Jackson 3 plugin and migrate publishing to maven-publish

[Sboti03]

What changed

Build and publishing

• upgraded the Gradle build setup
• migrated publishing from legacy maven / uploadArchives to maven-publish
• updated release workflows to use publish
• consolidated shared JUnit 5 and dependency configuration
• kept publishToMavenLocal working with the upgraded build

Jackson 3 support

• added a new java-snapshot-testing-plugin-jackson3 module
• introduced Jackson 3 serializer implementations and tests
• added snapshot fixtures for the new module
• updated the README with Jackson 2 vs Jackson 3 usage examples

Validation

Ran:

./gradlew publishToMavenLocal
./gradlew :java-snapshot-testing-plugin-jackson3:test publishToMavenLocal

Notes

• existing Java 8-targeted modules remain unchanged in intent
• Jackson 3 support is provided as a separate module rather than changing the existing Jackson 2 plugin
• the branch history is intentionally split into two commits for easier review

fixes #183

[jackmatt2]

Why is this long if else needed as it wasn't required previously? Will the code work without it?

[Sboti03]

The Jackson 3 module needs Java 17 because Jackson 3 artifacts require Java 17.
The long root if/else is not needed the default can stay Java 11 and Jackson 3 can override locally.

[Sboti03]

@jackmatt2 I've made the fixes you requested and fixed the pipelines.

[Sboti03]

When will this be released?

[jackmatt2]

When will this be released?

Hi @Sboti03. I'm reaching out to the company to update the maven central token as I think it's expired. Once that's done I can release immediately.

[Sboti03]

Hi @jackmatt2

I wanted to follow up on this. Has there been any progress with renewing the Maven Central token?

We're currently waiting for the release, so I'd appreciate any update on the status.

Thanks!

[jackmatt2]

Let me check again. If I still can't get it renewed I might need to consider an alternative.

[jackmatt2]

Hi @Sboti03

https://github.com/origin-energy/java-snapshot-testing/releases/tag/4.1.0

I have implemented Jitpack as a temporary solution until we get the credentials sorted.

See the README on how to add jitpack as a repository. Note that the dependency names have changed a little bit to conform to jitpack conventions.

Let me know how it goes.