gh-action: Upload snapshot as post-commit job

[yue9944882]

@brendandburns i added my jira account credentials and gpg keys in the repo secrets to push snapshots. github claims that these secrets are perfectly protected 🤞

if this works well, we can move the maven release job as another job triggered by simple git tags. so we don't need to deal with the fiddly release process manually anymore!

[brendandburns]

Thanks for doing this. Is there an example of where these snapshots end-up? e.g. what is the version?

[yue9944882]

@brendandburns they're pushed to sonatype oss snapshot repository, so developers can get quick access to the master branch package by adding the following repository to their pom.xml:

  <repositories>
    <repository>
      <id>oss.sonatype.org-snapshot</id>
      <url>http://oss.sonatype.org/content/repositories/snapshots</url>
      <releases>
        <enabled>false</enabled>
      </releases>
      <snapshots>
        <enabled>true</enabled>
      </snapshots>
    </repository>
  </repositories>

e.g. what is the version?

the snapshots are built from branch master, i added a badge to show the latest snapshot version. (the current uploaded snapshot package is pushed by myself manually)

[brendandburns]

/lgtm
/approve

Thanks for starting us towards GH action based automation!

[k8s-ci-robot]

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[brendandburns]

(we should probably expand this to the release branches also)