Add option to add and list ssh singing key for logged in user

[kousikmitra]

Fixes #7009

This will enhance the ssh-key add command with an option --type which will take any of the values [authentication, signing] as input, based on the value it will either add the ssh key as authentication key or a signing key. The default value for --type is authentication

Ex:

$ gh ssh-key add ./ssh_file.pub --type signing --title "Personal Signing Key"
✓ Public key added to your account

---

This will also enable ssh-key list command to also print the ssh singing keys given it has the required permission to do so.

Ex:

• When don't have oauth permission for ssh_signing_keys

$ gh ssh-key list

warning:  HTTP 404: Not Found (https://api.github.com/user/ssh_signing_keys?per_page=100)
This API operation needs the "admin:ssh_signing_key" scope. To request it, run:  gh auth refresh -h github.com -s admin:ssh_signing_key
TITLE   ID        KEY                    TYPE            ADDED
Laptop  12345678  ssh-ed25519 AAAAC3Nza  authentication  0m

• When have both of the oauth permission

$ gh ssh-key list

TITLE   ID        KEY                    TYPE            ADDED
Laptop  12345678  ssh-ed25519 AAAAC3Nza  authentication  5m
Laptop  12345     ssh-ed25519 AAAAC3Nza  signing         0m

[vilmibm]

What's here is great! thank you! In order to consider this complete though I'd love to see gh ssh-key list augmented to print out these signing keys, too.

A new column for type should be added to ssh-key list (added to the end for non-tty output) and signing keys included in the list.

Let me know if this is for some reason not possible.

[kousikmitra]

What's here is great! thank you! In order to consider this complete though I'd love to see gh ssh-key list augmented to print out these signing keys, too.

A new column for type should be added to ssh-key list (added to the end for non-tty output) and signing keys included in the list.

Let me know if this is for some reason not possible.

I have mentioned it here If you suggest to go ahead with this I will add changes here.

[vilmibm]

awesome work, thank you again.