Allow users to add multiple MFA devices

[NHAS]

Users should be able to add multiple MFA devices so they arent immediately locked out on MFA device loss.

• [ ] Should be limitable by configuration (i.e users should be able to have 1 to n MFA options)
• [ ] Needs UI page

Currently the only way to do this is by adding another wireguard device, which is not ideal for single user deployments.