keepassxc-cli: handle attachments

[grcancelliere]

Summary

Being able to work with attachments in entries from the CLI.

Desired Behavior

• the add command should have switches to add attachments by path
• the edit command should have switches to add attachments by path or remove attachments by name
• the cli should have a command (getattachment ?) to export an attachment from an entry by name

Possible Solution

Context

I'd like to use the CLI to automate the handling of secure files (e.g. SSH keys, GPG keys, ...) by storing them in Keepass entries.

[hifi]

Just a note that you can use SSH keys from within KeePassXC with the SSH Agent feature.

[mmaridev]

+1 would be really useful to automate SSH private keys generation

[mStirner]

I stubled across this issue.
It would be really nice to work with attachments from the cli, like open/edit/delete/add/export.