Feat/os keychain followup - #1770

@willemneal

... it's possible to have the name used in keys add differ from what is used in entry-name?

Good call! Yeah, at the moment, this is possible. It still ends up working because we are saving the value of --entry-name in the <NAME>.toml file, like this: entry_name = "secure_store:org.stellar.cli-<NAME>. And then getting that entry_name from the toml file when accessing the public key, or using the private key.

Though, this may be confusing. 🤔

Instead, we could remove the --entry-name flag, and when adding a new key, require that the key name is the same as the entry name in the OS's secure store. So, this command would change to be: cargo run keys add alice.

But, now I'm starting to wonder if we shouldn't allow users to add keys from the keychain at all. If we do, we'd need to make sure that users add the keys to their secure store with:

1. the key name prepended with secure_store:org.stellar.cli-
2. the key saved as a base64 encoded ed25519_dalek::SigningKey

And we could probably do that, but I'm not sure how necessary this feature is. 🤔

Since we are now planning to store the seed phrase instead of the signing key in the OS secure storage, I think that a more useful feature would be to allow a user to add a new key with their seed phrase, which is saved in secure storage instead of in the local file. So the command could look like this:

cargo run keys add <NAME> --secure-store

which would then prompt the user to enter their seed phrase:

Type a 12/24 word seed phrase:
...

🎉