- `checksum@1.0.0` is a thin wrapper over node's own crypto module. Node can do this without a dependency.
- The lockfile carried an extra copy of `optimist` (0.3.7) only for that wrapper.
- Removes `checksum` from the `fxa-profile-server` package.json and from yarn.lock.
- Computes the `/profile` ETag with `crypto.hash('sha1', JSON.stringify(profile), 'hex')` in `profile.js`.
- Computes the `/display_name` ETag the same way in `display_name/get.js`.
- Pins the expected ETag in the `should return a displayName` test, so a change of hash algorithm, encoding, or header format fails.
Closes: https://mozilla-hub.atlassian.net/browse/FXA-13927