Maintainers are not cc to an issue or a pullRequest when they are already participants

[nicolasgras]

This pull request resolves #143.

Before cc maintainers to an issue or a pull request, participants of it are queried with Github GraphQL Api and are removed of list of maintainers that are notified.

The GraphQL request body is:

query($owner: String! $repoName: String! $prNumber: Int!) {
  repository(owner: $owner, name: $repoName) {
    $objectType(number: $number) {
      participants(first: 50) {
        edges {
          node {
            login
          }
        }
      }
    }
  }
}

where $objectType is replaced by issue or pullRequest according to the situation.

[nicolasgras]

You're welcome!

[gsmet]

I had to do some rather involved surgery when rebasing on top of https://github.com/quarkusio/quarkus-github-bot/pull/299 .

Could you check it still makes sense to you? I refactored things a bit to fit with the new Mentions object but I think it should be good enough.

[gsmet]

While doing that, I also saw that we missed a few places to use the new Mentions pattern so I cleaned things up in all places.

[nicolasgras]

Thank you for having updated the branch. Yes, it still makes sense for me.

[gsmet]

Thanks for checking, I merged it!