Add SSH key embedding and dev.sh SSH mounting for development

[Lemmons]

I don't think this is particularly in the correct place, but I wasn't sure what the best approach was here. While working on the rfid ui I wanted a way to be able to be a little more hands off when updating firmware using the update-firmware script. This is the best I was able to come up with. I assume there is a much better way to do this though (I imagine if we do want to keep the ability bake in ssh keys, it should go in the devel overlays, rather than common). Definitely would like to get feedback on how we can make the iteration process faster when you need to push new versions to a real machine, and will be happy to update this as needed to match what that process might be.

Changes

• Add overlays/common/04-ssh-authorized-keys/ overlay for embedding SSH public keys
• Add SSH folder mounting to dev.sh for container development
• Update .gitignore to exclude personal SSH keys
• Update upgrade-firmware.sh to remove the ssh host from known hosts, as it will fail due to the firmware upgrade changing the host sha

[mcristina422]

I like what you're going for here, I end up doing the same thing manually.
I think long term, we should reconfigure dropbear SSH server to save and reuse it's SSH Host Keys in a persistent mount point, so its not regenerated every upgrade

[paxx12]

@Lemmons

I get the idea, but until there are fixed credentials on printer this is also not needed. For example this is what I'm doing:

sshpass -p snapmaker ssh-copy-id root@u1eth.home && ./scripts/dev/upgrade-firmware.sh root@u1eth.home extended

[paxx12]

@Lemmons

I think all of those could be folded into providing overlays/devel/local-overlay where we would generate the ssh_host_key and ssh_public_keys. Kind of having a space to put whatever local amendments are needed. The script could generate all of those and put it into expected data structure (scripts/dev/generate-dev-keys.sh). So:

overlays/devel/local-overlay/root/etc/ssh/ssh_host_key*
overlays/devel/local-overlay/root/root/.ssh/authorized_keys
overlays/devel/local-overlay/root/root/.ssh/id_{rsa,ecdsa}{,.pub}

Create ssh_config to allow using those generated keys for all operations in dev.sh container, the dev.sh could maybe even generate those keys for the first time.

[paxx12]

Replaced by #222 there's also the #208.