[FastAPI] Implement User authentication

Before we can implement Package-based routes, we need the ability to login and manage user accounts. This issue is here to track progress on user authentication in the FastAPI port.

• /register
• /passreset
• /login
• /logout
• /account/<username>

This issue will be updated as routes are merged into pu.

changed milestone to %Python/FastAPI

added fastapi label

marked the checklist item /register as completed

marked the checklist item /login as completed

marked the checklist item /passreset as completed

marked the checklist item /logout as completed

marked the checklist item /account/<username> as completed

Merged: !29 (merged)

closed