Change `Repository`'s `attributedTo` to list of usernames?

[penyuan]

Right now for GitHub repositories, the attributedTo field for its Repository is the owner part of the slug (i.e. OPEN-NEXT in OPEN-NEXT/wp2.2_dev) which is clearly not always an actual GitHub user.

So, make attributedTo a Python list that holds actual usernames.

This might affect downstream analyses and visualisations.

[penyuan]

WARNING: It will indeed affect downstream code. Right now attributedTo is the equivalent of the GitHub repository owner or Wikifactory project, and this is used by dash_app.py to populate the project and repository selections from the URL.

If we want a list of, e.g. users who created or are the "author" of a repository, adding another custom field might be safe.