Add introducer add command

- Create a command to add an introducer (with domains).
- Add a module for escaping regular expressions used in certifications
- Add some helper functions.

src/commands.rs

@@ -1,5 +1,7 @@
 use anyhow::Result;
 
+use sequoia_openpgp::Fingerprint;
+
 use crate::commands;
 use crate::cli::cli_args::{CliArgs, HuskSubcommands};
 use crate::config::HuskConfigContainer;
@@ -8,6 +10,14 @@ pub mod daemon;
 pub mod introducer;
 pub mod local;
 
+#[derive(thiserror::Error, Debug)]
+pub enum CommandError {
+    #[error("Certificate not found: {0}")]
+    CertNotFound(Fingerprint),
+    #[error("List of domains is empty")]
+    DomainListEmpty,
+}
+
 pub async fn dispatch(cli: CliArgs, config: HuskConfigContainer) -> Result<()> {
 
     match cli.subcommand {