Allow signed releases to Artifactory from GitHub Actions about reactor

[simonbasle]

Gradle custom task to qualify the version (this task correctly parses qualifiers of old scheme milestones and release candidates with the dot separator, as well as dash separator):

import org.gradle.util.VersionNumber

def qualifyVersion(String v) {
  def versionNumber = VersionNumber.parse(v)

  if (versionNumber == VersionNumber.UNKNOWN) return "BAD";
  
  if (versionNumber.qualifier == null || versionNumber.qualifier.size() == 0) return "RELEASE" //new scheme
  if (versionNumber.qualifier == "RELEASE") return "RELEASE" //old scheme
  if (versionNumber.qualifier.matches("(?:M|RC)\\d+")) return "MILESTONE"
  if (versionNumber.qualifier == "SNAPSHOT" || versionNumber.qualifier == "BUILD-SNAPSHOT") return "SNAPSHOT"
  
  return "BAD"
}

task qualifyVersionGha() {
  def versionType = qualifyVersion(version)

  if (versionType == "BAD") {
    println "::warning ::Unable to parse $version to a VersionNumber with recognizable qualifier"
  }
  
  println "::set-output name=versionType::$versionType"
  println "::set-output name=fullVersion::$version"
}

[simonbasle]

While evaluating this solution, a few things that came up for consideration:

• the artifactory and signing plugins are only loaded if relevant credentials are accessible
• since we'd like to draft releases notes earlier than currently, it doesn't make much sense to use the tag-and-release action. git commands should work thanks to checkout@v2 so we use git tag command
• some projects have artifacts that get rejected by Maven Central (eg. docs zip) so we need to differentiate between what goes to Artifactory (everything) and what goes to Central (the MavenJavaPublication)

[simonbasle]

TODO by May's release:

• reactor-kafka
• reactor-rabbitmq
• reactor-kotlin-extensions
• create gha environments for the above
• disable Bamboo plans for the above + disable their dysprosium branch plan as well

[simonbasle]

This migration is complete as of 2021/04/14