Add Two Factor connector

[tharsheblows]

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Fixes #1386

This adds the Two Factor plugin connector. It is based on WP.org's connector here with minor changes: it removes the WebAuthn plugin actions and logs when the provider is initially added by a user.

The core actions, eg updating a user profile and logging in, are still logged, this does not replace those:

Checklist

• [x] Project documentation has been updated to reflect the changes in this pull request, if applicable.
• [x] I have tested the changes in the local development environment (see contributing.md).
• [x] I have added phpunit tests.

Release Changelog

• Feature: Add Two Factor connector