## Problem
`secrets.GITHUB_TOKEN` (with any permissions) is not enough to get
a user's membership info if they decide to hide it.
## Summary of changes
- Use `secrets.CI_ACCESS_TOKEN` for `gh api` call
- Use `pull_request_target` instead of `pull_request` event to get
access to secrets
## Problem
`author_association` doesn't properly work if a GitHub user decides not
to show affiliation with the org in their profile (i.e. if it's private)
## Summary of changes
- Call
`/orgs/ORG/members/USERNAME` API to check whether
a PR/issue author is a member of the org
## Problem
We want to mark new PRs and issues created by external users
## Summary of changes
- Add a new workflow which adds `external` label for issues and PRs
created by external users