Introduce Code Owners

GitLab supports something called Code Owners.

In short, this would allow us to:

• add people or groups as Code Owners to specific files/directories
• Require owners to approve changes
• Identify the owners, since Code Owner names are displayed on the files and directories they own

Why is this beneficial to us? It:

• ensures quality: it allows us to define the users who have domain expertise for specific paths in the repository. By doing so, we can help keep out code that does not fill well in those parts by ensuring people who know that part of the code will have a look at it
• helps guide merge request creators to the correct set of reviewers
• helps developers know who to ask questions to on specific parts of the code base

Of course we don't need to do this for every single directory, but given the different areas of expertise we have in the team it makes sense to do this for some parts of what we have now.