Add automated release and publish to OSS Sonatype via GitHub Actions

[Copilot]

Implements automated Maven Central publishing using GitHub Actions workflow, replacing manual release process. Based on loxone-client-kotlin reference implementation.

Build Configuration

• Version management: axion-release v1.14.4 derives versions from git tags (replaces hardcoded gradle.properties)
• Publishing: nexus-publish v1.3.0 automates Sonatype staging repository lifecycle
• Signing: In-memory PGP keys from environment variables (CI/CD), backward compatible with properties file (local dev)
• Compatibility: Gradle 7.5.1, Java 11 (no upgrades)

GitHub Actions Workflow

.github/workflows/loxone-java-release.yml - Manual trigger with semantic version increment:

on:
  workflow_dispatch:
    inputs:
      versionIncrement:
        type: choice
        options: [incrementPatch, incrementMinor, incrementMajor]

Pipeline: tag creation → build → GPG sign → Sonatype publish → staging close/release → Maven Central (~10min)

Required Secrets

Repository secrets must be configured before first release:

Secret	Purpose
OSS_USER / OSS_PASS	Sonatype OSSRH credentials
SIGNING_KEY / SIGNING_PASS	GPG key (base64) and passphrase
SMARTEON_GIT_TOKEN	GitHub PAT for tag push

Documentation

• RELEASE_SETUP.md: Prerequisites, GPG setup, Sonatype account configuration
• ENVIRONMENT_VARIABLES.md: Secret descriptions, security warnings, local testing

See RELEASE_SETUP.md for complete setup instructions.

Original prompt

Please add automated release and publish to OSS sonatype repository using github actions. You can use the example of https://github.com/Smarteon/loxone-client-kotlin. Please also double check the gradle setup and summarize all the environemnt needed to be set. Note that this project is using older gradle - preferrably do not upgrade.

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[jimirocks]

@copilot good job please look at comments and adjust