[LightDM] Perform non-interactive login using provided uses credentials

[arijo]

Hi list,

I would like to discuss the possibility of performing a login in a 
non-interactive way using full user credentials as if they were input 
into the greeter dialog.
Our current setups occasionally allows us to know about user identity 
and credentials as soon as initramfs, so it is somewhat unnecessary to 
ask the user to input them again.
I would like to avoid using the auto-login feature as is, because it 
prevents the unlocking of encrypted homes, keyrings and such. I am a bit 
unsure how to tell lightdm about existing credentials (I'm pretty sure 
it is impossible using the current code base), so I would appreciate any 
input from experienced developers on how to address this before I start 
hacking on the code.

--
Arijo