Option to use author instead of commiter in declarative pipeline

Problem
Right now when adding a GitHub source in Blue Ocean every change merged from a pull request is being shown as "Changes from noreply". This also impacts all plugins that rely on the commiters for a build since it effectively hides the actual authors (including when using `email-ext` or `mailer`).

Since changing the default behaviour might be a breaking change, an option should be added to the pipeline so that each agent uses the correct strategy for the checkout.

(in `git-plugin` this is called `AuthorInChangelog`)

Scope

• Switch to displaying the Author information for Git repositories (instead of Committer)