Allow users to configure the TOTP Algorithm and Digits. This should be used with caution as many TOTP applications do not support it. Some will also fail to notify the user that there is an issue. i.e. if the algorithm in the QR code is sha512, they continue to generate one time passwords with sha1. In addition this drastically refactors TOTP in general to be more user friendly by not forcing them to register a new device if the administrator changes the period (or algorithm).
Fixes#1226.
Allow users to select and save the preferred duo device and method, depending on availability in the duo account. A default enrollment URL is provided and adjusted if returned by the duo API. This allows auto-enrollment if enabled by the administrator.
Closes#594. Closes#1039.
