[enhancement] Forward text printed by PAM

[chiraag-nataraj]

As part of my general security-conscious setup, I have enabled libpam-u2f so that I get prompted to touch my Yubikey after I enter my password (as a second factor). I have enabled the cue option just for additional feedback, which works well on the terminal (it prints "Please touch the device." by default, but that's configurable using the cue_prompt option). However, when I lock the screen with swaylock, I simply get a Verifying text and the cue prompt never shows up.

It would be nice if this (and any other text printed out by PAM during authentication) were directly forwarded to the lock screen (potentially as a configurable option for those who don't want it). Ideally, any additional input (à la libpam-otpw) would also be captured and forwarded like the original password.

[hendursaga]

I could test any patches with my Solo key (v2) once it arrives!