This PR builds on top of #863 so it would be best to merge that first.

This PR adds Magic Link + Passkey authentication.

Types of changes
What types of changes does your code introduce? Put an x in all the boxes that apply:

• New feature (non-breaking change which adds functionality)

Checklist
Go over all the following points, and put an x in all the boxes that apply:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I am aware that this is an nbdev project, and I have edited, cleaned, and synced the source notebooks instead of editing .py or .md files directly.