Add dns_update_cmd to the CLI

src/config.rs

@@ -28,6 +28,8 @@ pub struct Config {
 	cryptoperiod: NonZeroU64,
 	#[arg(short, long, default_value_t = 1728000)]
 	revocation: u64,
+	#[arg(short = 'u', long)]
+	dns_update_cmd: String,
 	#[arg(short = 'x', long, default_value_t = 1296000)]
 	expiration: u64,
 	#[arg(short, long, action = clap::ArgAction::Count)]
@@ -55,6 +57,10 @@ impl Config {
 		self.cryptoperiod
 	}
 
+	pub fn dns_update_cmd(&self) -> &str {
+		&self.dns_update_cmd
+	}
+
 	pub fn domains(&self) -> &[String] {
 		&self.domain
 	}