### Summary
I'm fixing one or more of the following CI/CD misconfigurations to
improve security. Please feel free to leave a comment if you think the
current permissions for the GITHUB_TOKEN should not be restricted so I
can take a note of it as accepted behaviour.
- Restrict permissions for GITHUB_TOKEN
- Add step-security/harden-runner
- Pin Actions to a full length commit SHA
### Security Fixes
will fix https://github.com/neondatabase/cloud/issues/26141
## Problem
One of the PRs opened by a `neondatabase` org member got labelled as
`external` because the `gh api` call failed in the wrong way:
```
Get "https://api.github.com/orgs/neondatabase/members/<username>": dial tcp 140.82.114.5:443: i/o timeout
is-member=false
```
## Summary of changes
- Check that the error message is expected before labelling PRs
- Retry `gh api` call for 10 times in case of unexpected error messages
- Add `workflow_dispatch` trigger
## 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
