User management

• Decide what data we need to store for a user (first name, last name, email, date of registration, company/organization etc.). But we need to make registration as simple as possible, so probably only ask for first name, last name, email, password in the main registration form and then give options to fill out additional info.
• Require min 12 character long random passwords
• Implement user roles so that we have sandbox and paying users, where the sandbox users can only access the sandbox data.
• Register new user with registration form
• Send and handle account confirmation email to verify email address so that we can send bills
• Delete a user
• Generate and manage API keys for a user ? So that one user can have multiple API keys and they don't need to send their user account password in each request...Probably with os.urandom(24) as per https://realpython.com/token-based-authentication-with-flask/.

See Ch8 User Authentication (esp New User Registration, Account Confirmation) in Flask Web Development 2e

No files, tests, or entry points are named; start by reviewing the existing Flask application structure and the referenced Flask Web Development 2e chapter. The scope must be clarified and decomposed before implementation, with completion covering registration, confirmation email, password rules, roles, deletion, and API-key management.