[GitHub REST/Webhook API] `author_association` returns different value than the web UI

[Urgau]

While analyzing why triagebot (our bot) commented this message, while it shouldn't as the PR author is a member of the rust-lang organization (as can be seen on the web UI), we came across this issue.

Looking at the webhook event we got from the previous comment, we can see that the issue.author_association is set at CONTRIBUTOR, not to be confused by the author of the comment who's author_association is correctly set at MEMBER.

However we can see on the web UI that @Kobzol is a member of the rust-lang organization, we would therefor expect the issue.author_association to be MEMBER instead of CONTRIBUTOR as:

MEMBER: The author is a member of the organization that owns the repository.

This can be reproduced using the REST pulls endpoint, https://api.github.com/repos/rust-lang/rust/pulls/143316:

{
  // ...
  "author_association": "CONTRIBUTOR",
}

It seems like other people have noticed the same bug, community#18690.

[Urgau]

As mentioned in https://github.com/orgs/community/discussions/18690#discussioncomment-4232389 it's linked to the author membership status (private/public) to the organization.

If it's private then the webhook and unauthenticated API request return CONTRIBUTOR instead of MEMBER with authenticated API requests.