I added a new CLI to send qrcode otp email to the user to improve user experience.
Generally, the qrcode image is generated once the user account is created. Hence, make up approaches are also provided for older users that don't have third-party otp secret or qrcode image.
After running the command: localdb qrcode <username>, the email will be sent to the user's email address.

Users can retrieve the 6-digit otp in authenticator apps by scanning the qrcode on their phone.

I tested the sending email function with the following scenario:

1. normal usage

2. wrong username/invalid user/non-existing user

3. no email address for the existing user

4. normal usage but the existing user does not have a pre-generated qrcode image

5. normal usage but the existing user does not have a third-party OTP secret and a pre-generated qrcode image