Add signkey create

- Add a CLI command for creating a new signing key.

src/commands/signkey/create.rs

@@ -0,0 +1,35 @@
+//! signkey create command
+
+use std::path::PathBuf;
+
+use anyhow::Result;
+use sequoia_openpgp::cert::CertBuilder;
+use sequoia_directories::Home;
+
+use crate::cli::cli_args::SignkeyCreateCommand;
+use crate::common::crypto;
+use crate::config::{HuskConfig, HuskConfigContainer};
+use crate::types::husk_context::HuskContext;
+
+pub async fn dispatch(cmd: SignkeyCreateCommand, config: HuskConfigContainer)
+    -> Result<()> {
+
+    let config: HuskConfig = config.into();
+    let context = HuskContext::new(&config)?;
+    let sequoia_home = Home::new(PathBuf::from(&config.sequoia_home))?;
+
+    // XXX: cleanup the userid before using
+    let (cert, _) = CertBuilder::new()
+        .add_signing_subkey()
+        .add_userid(cmd.userid)
+        .generate()?;
+
+    if crypto::import_key(sequoia_home, &cert) {
+        let vc = cert.with_policy(&context.policy, None)?;
+        crypto::set_signing_key(&context, &vc)?;
+
+        println!("New signing key: {}", vc.fingerprint());
+    }
+
+    Ok(())
+}