refactor: replace internal authentication plugin with NPM installed plugin-authentication

[kieckhafer]

Impact: minor
Type: refactor

This PR removes the authentication plugin code from the API, and installs the @reactioncommerce/plugin-authentication to perform the same functions.

Breaking changes

None

Testing

The authentication code is the same as it was before, it's just being installed from a different place, so you should see nothing different in the behavior of this PR and the v3.1.0 release it was created from.

1. Start the API
2. Create a user
3. Create a shop
4. See that you can reset your password. The mutations here are meant to be internally called, so you need to reset through Identity.

[focusaurus]

Code changes look good. If you want me to test locally mention me again and I'll allocate 30m to do it, but I haven't had a full system running locally recently so it's not super fast for me to test.

[mikemurray]

👍