feat: specify repo gpg when not inside repo

[gboutry]

Summary

Add the possibility to specify an external gpg key to a RHEL repo.

Motivation

To install Jenkins with its official repository, I need to import manually a key since it's not in the repo configuration

Link to RHEL documentation: https://www.jenkins.io/doc/book/installing/linux/#red-hat-centos

Alternative

I'm currently doing the following:

await @file.download
  $header: "Download jenkins repo's signing key"
  $unless_exists: "/tmp/jenkins.io.key"
  source: "https://pkg.jenkins.io/redhat/jenkins.io.key"
  target: "/tmp/jenkins.io.key"
await @execute
  $header: "Install jenkins repo's signing key"
  command: "rpm --import-key /tmp/jenkins.io.key"
await @tools.repo
  $header: "Setup jenkins repo"
  $unless_exists: "/etc/yum.repos.d/jenkins.repo"
  source: "https://pkg.jenkins.io/redhat-stable/jenkins.repo"
  target: "/etc/yum.repos.d/jenkins.repo"
  verify: false

Draft

I would like the following API:

  await @tools.repo
    $header: "Setup jenkins repo"
    source: "https://pkg.jenkins.io/redhat-stable/jenkins.repo"
    gpg_key: "https://pkg.jenkins.io/redhat/jenkins.io.key"
    target: "/etc/yum.repos.d/jenkins.repo"
    verify: true