Handle multiple fingerprints

[ghost]

Since Ubuntu developers are working with the libfprint project to improve support for biometric authentication methods in GNOME-based Linux distros, it's necessary to create a solution to implement this feature in elementary OS. I've prepared some mock-ups for the fingerprint configuration flow.

Click to expand

I also attached the source Figma file so that everyone can contribute:
Figma Mock-up

[danirabbit]

I feel like maybe we should directly list enrolled authentication methods in the "Locking" tab. This would do a few things:

• Seeing which fingers you've enrolled already would ensure you don't add the same finger multiple times
• We wouldn't need the "success" screen since the positive feedback would be another entry appearing in the list
• It doesn't look like there's a way to remove enrolled fingerprints in this design, so a list would account for that

@danrabbit, something like that?

Click to expand

The list contains all added authentication methods that can be managed manually (rename, delete). After clicking on the add button, a pop-up window will appear to select the preferred authentication method. If a fingerprint scanner is selected, the setup process begins (steps 2 and 3). The "success" screen can be replaced with a simple icon in the list that remains until user close the settings or select another menu.

[danirabbit]

Closing since fingerprint enrollment was adding to User settings in #256

[danirabbit]

Actually I'm going to reopen this and move it to user settings because it has some cool design for dealing with multiple auth methods