[Feature Request] With a global notify trigger for the Agola pipe building

Add a feature: a trigger with failure in each step or final pipe suc result, then trigger a shell command to outside, for mail or message nofity, just like:

  runs: [
      name: 'agola build/test',
      tasks: [
        task_build_go(version, arch)
        for version in ['1.11', '1.12']
        for arch in ['amd64', 'arm64']
      ] ...
  triggers(code, msg):[
      name: 'failure notify',
      type: step_failure,
      shell: 'sh fail.sh $code "$msg"',//call mail, msg nofify: fail alert with errCode and message
      name: 'success notify',
      type: build_finished,
      shell: 'sh suc.sh $code ',//call mail, msg nofify: success!


Update: This shouldn’t be shell out, but be notification config/key(email, msg, …)
Notify in notification module with a default notify key, and if set in config.jsonnet then use it instead of the default.