Bumps commons-io:commons-io from 2.17.0 to 2.18.0.

---
updated-dependencies:
- dependency-name: commons-io:commons-io
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

PR for MGPG-130 updated the defaults, but this documentation
was left out and may cause confusion.

Bumps [org.simplify4u.plugins:pgpverify-maven-plugin](https://github.com/s4u/pgpverify-maven-plugin) from 1.18.2 to 1.19.1.
- [Release notes](https://github.com/s4u/pgpverify-maven-plugin/releases)
- [Commits](s4u/pgpverify-maven-plugin@v1.18.2...v1.19.1)

---
updated-dependencies:
- dependency-name: org.simplify4u.plugins:pgpverify-maven-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

#125)

Bumps [org.apache.maven.plugins:maven-invoker-plugin](https://github.com/apache/maven-invoker-plugin) from 3.8.0 to 3.9.0.
- [Release notes](https://github.com/apache/maven-invoker-plugin/releases)
- [Commits](apache/maven-invoker-plugin@maven-invoker-plugin-3.8.0...maven-invoker-plugin-3.9.0)

---
updated-dependencies:
- dependency-name: org.apache.maven.plugins:maven-invoker-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps commons-io:commons-io from 2.18.0 to 2.19.0.

---
updated-dependencies:
- dependency-name: commons-io:commons-io
  dependency-version: 2.19.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps `bouncycastleVersion` from 1.78.1 to 1.80.

Updates `org.bouncycastle:bcpg-jdk18on` from 1.78.1 to 1.80
- [Changelog](https://github.com/bcgit/bc-java/blob/main/docs/releasenotes.html)
- [Commits](https://github.com/bcgit/bc-java/commits)

Updates `org.bouncycastle:bcprov-jdk18on` from 1.78.1 to 1.80
- [Changelog](https://github.com/bcgit/bc-java/blob/main/docs/releasenotes.html)
- [Commits](https://github.com/bcgit/bc-java/commits)

Updates `org.bouncycastle:bcutil-jdk18on` from 1.78.1 to 1.80
- [Changelog](https://github.com/bcgit/bc-java/blob/main/docs/releasenotes.html)
- [Commits](https://github.com/bcgit/bc-java/commits)

---
updated-dependencies:
- dependency-name: org.bouncycastle:bcpg-jdk18on
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.bouncycastle:bcprov-jdk18on
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.bouncycastle:bcutil-jdk18on
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

And related fixes:
* POM add missing deps
* move to Maven 3 p-u, drop p-x
* test: checkstyle fixes

And be consistent: as some legacy stuff in Maven and around (plugins) perform just nullcheck and not also empty string check, and get confused on empty string classifier. Plugins are (should) not be reused as dependencies, so despite the helper class is `public` I see no harm to alter it.

Supersedes #135 
Fixes #138