Chore/migrate workflow to mvn central

[ortizjeronimo]

Why

• OSSRH is deprecated; Sonatype Central Portal is the current path.
• Old [email protected] couldn’t import GPG keys and relied on legacy defaults.

What changed

Build & Publish

• Added org.sonatype.central:central-publishing-maven-plugin to pom.xml.
• Removed legacy OSSRH staging flow (nexus-staging-maven-plugin) and any distributionManagement pointing to ossrh.
• Kept required attachers: maven-source-plugin, maven-javadoc-plugin, maven-gpg-plugin.

GitHub Actions

• Upgraded to actions/setup-java@v4.
• Explicitly set OpenJDK distribution to Temurin.
• Wired Central creds directly in setup-java@v4 so no wrapper envs are needed at deploy time.
• Deploy step runs only on tags v*.

Settings

• settings.xml: switched server id from ossrh → central.
• Credentials and passphrase are still provided via GitHub secrets (no secrets in repo).

Security

• Secrets used: OSSRH_USER_TOKEN, OSSRH_PWD_TOKEN (now holding Central Portal token pair), GPG_SIGNING_KEY (base64, ascii-armored), GPG_PWD.
• Secrets remain masked and are only consumed on the runner.

Developer impact

• No code changes required to consume the library.
• Local builds unchanged; to publish locally you still run mvn deploy (with proper settings.xml and keyring).

CI behavior after merge

• Every push builds & tests.
• Publish to Maven Central occurs only when pushing a tag starting with v (e.g., v0.12.1).

To do

• Update secrets names to avoid confusion