Utilize Co-authored-by convention in UX

Description

Git commits often have several authors and under the current workflow, authors are forced to decide who will be the git "Author" on a commit. For pair programming and mentor/mentee style programming, this can make attributing a commit visually within gitlab difficult. There are conventions for attributing co-authors but they are external to git itself.

Proposal

Similar to how gitlab parses the message body for issues references, Gitlab should recognize Co-Authored-By: [name] <[email]> in the message body, and should display user icons on UI related to the commit. Here is an example commit message:

commit ae878fc8b9761d099a4145617e4a48cbeb390623
  Author: Foo Bar <x@y.com>
  Date:   Fri Jun 1 01:44:02 2012 +0000

    Refactor gitlab to support co-authors

     * Do awesome work
     * Make an awesome product
     * Be better than the competition

    Fixes: #[number redacted]
    Co-Authored-By: Spam King <x@y.com>
    Co-Authored-By: Monty Python <x@y.com>

I work at a shop that does a lot of pair programming and this would be a huge boon to a pair-driven workflow. We frequently encounter mis-attributed commits and having the UX in gitlab support a co-author workflow would significantly improve code reviews and our ability to visually git blame and followup on changes.

I have chosen the "Co-Authored-By:" naming scheme from previous standards that I encountered while researching this topic.

Links / references

Documentation blurb

If your commit has additional authors or people who helped in creating the commit, you can make their contributions known in the gitlab UI by putting Co-Authored-By: [name] <[email]> on it's own line within the body of your commit message.