Allow using lock screen code with "Biometric unlock"

[Ajedi32]

Right now, when you enable the "Biometric unlock" feature you can unlock Aegis using your fingerprint, but if your fingerprint is for whatever reason unreadable (wet, wearing gloves, etc) the only alternative is to enter the full encryption database password.

If I'm understanding the Android developer documentation right, this behavior can be rather easily altered to allow unlocking using your PIN as an alternative if you include KeyProperties.AUTH_DEVICE_CREDENTIAL when calling setUserAuthenticationParameters().

This could be implemented as a separate "PIN/Pattern Unlock" toggle, or alternately we could just make it the default and rename "Biometric unlock" to "Device credential unlock" or something to that effect.

[Lanchon]

the user should be able to select:

• any unlock method including biometrics
• main unlock method excluding biometrics

biometrics only does not make much sense, but to each is own.

[Ajedi32]

Checked the code and it seems like the relevant line is here:

Aegis/app/src/main/java/com/beemdevelopment/aegis/crypto/KeyStoreHandle.java

Line 51 in 59d5c64

.setUserAuthenticationRequired(true)

I'm guessing if you added this right after that line it would likely resolve this issue:

.setUserAuthenticationParameters(0, KeyProperties.AUTH_BIOMETRIC_STRONG | KeyProperties.AUTH_DEVICE_CREDENTIAL)

I'd submit it as a PR but I don't really have time right now to figure out how to build and test the app, and there's a bit more work needed to reword some text in UI and possibly implement settings to allow PIN auth without biometrics.