`cog login` fails silently if `pass` is uninitialized

Ran into an issue and thought I'd leave the solution here for incorporation into docs.

I had to spin up a machine on Google Cloud to build & test a Cog model. It's running Debian 10:

c0-deeplearning-common-cu110-v20221107-debian-10
Google, Debian 10 based Deep Learning VM with , M100, Base CUDA 11.0, Deep Learning VM Image with CUDA 11.0 preinstalled.

ck@cog-p4:~/cog-pyannote/speaker-diarization$ cog login
This command will authenticate Docker with Replicate's 'r8.im' Docker registry. You will need a Replicate account.

Hit enter to get started. A browser will open with an authentication token that you need to paste here.

If it didn't open automatically, open this URL in a web browser:
https://replicate.com/auth/token

Once you've signed in, copy the authentication token from that web page, paste it here, then hit enter:
SNIPPED_TOKEN
ⅹ Failed to run docker-credential-desktop: exit status 1
ck@cog-p4:~/cog-pyannote/speaker-diarization$ docker-credential-store store

I found the underlying issue by calling docker-credential-desktop directly with

docker-credential-desktop store
{"Username":"cameronk","Secret":"SNIPPED_TOKEN","ServerURL":"r8.im"}
error storing credentials - err: exit status 1, out: `pass not initialized: exit status 1`

Turns out this is because pass is not initialized. Solution:

1. gpg --generate-key
2. grab gpg id
3. pass init [gpg_id]
4. re-run cog login

Reference: https://github.com/docker/docker-credential-helpers/issues/102#issuecomment-388634452

Start with the documentation for the cog login entry point and review the reported Docker credential failure on Debian 10. Document the prerequisite gpg --generate-key and pass init [gpg_id] steps so users can authenticate successfully when pass is uninitialized.