Extend GitHub actions for automated publishing to oss.sonatype.org

[FDelporte]

Extend GitHub actions for automated publishing to oss.sonatype.org

[savageautomate]

This item has been completed using the new "Continuous Integration" workflow action.

• https://github.com/Pi4J/pi4j-v2/actions/workflows/ci.yml
• https://github.com/Pi4J/pi4j-v2/blob/main/.github/workflows/ci.yml

The first step is to use Maven to BUILD, TEST and DEPLOY build SNAPSHOT artifacts to the OSS Nexus Maven Repository.
(https://oss.sonatype.org/content/repositories/snapshots/com/pi4j/)

If successful, the second step is to deploy (add or update) the build SNAPSHOT packages (*.DEB & *.ZIP) to the Pi4J APT/Download Repository (https://github.com/Pi4J/download)

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Note: All build steps must succeed for this process to complete successfully. This includes compiling native code, compiling Java code, JavaDoc, unit testing, packaging and deploying.

Note: the necessary secrets (OSS Maven Repo & Github access credentials) are stored at the Pi4J Organizational unit in GitHub.