Log certificate domains before and after renewal

Right now only the id is logged as a prefix (e.g. crt-3), so it's not
possible to easily determine *which* certificate was renewed, or failed
to renew.

acmed/src/acme_proto.rs

@@ -210,6 +210,6 @@ pub fn request_certificate(cert: &Certificate, root_certs: &[String]) -> Result<
     let (crt, _) = http::get_certificate(cert, root_certs, &crt_url, &data_builder, &nonce)?;
     storage::write_certificate(cert, &crt.as_bytes())?;
 
-    cert.info("Certificate renewed");
+    cert.info(&format!("Certificate renewed (domains: {})", cert.domain_list()));
     Ok(())
 }

acmed/src/certificate.rs

@@ -105,7 +105,7 @@ impl Certificate {
 
     fn is_expiring(&self, cert: &X509Certificate) -> Result<bool, Error> {
         let expires_in = cert.expires_in()?;
-        self.debug(&format!("expires in {} days", expires_in.as_secs() / 86400));
+        self.debug(&format!("Certificate expires in {} days", expires_in.as_secs() / 86400));
         // TODO: allow a custom duration (using time-parse ?)
         // 1814400 is 3 weeks (3 * 7 * 24 * 60 * 60)
         let renewal_time = Duration::new(1_814_400, 0);
@@ -134,7 +134,17 @@ impl Certificate {
         has_miss
     }
 
+    /// Return a comma-separated list of the domains this certificate is valid for.
+    pub fn domain_list(&self) -> String {
+        self.domains
+            .iter()
+            .map(|domain| &*domain.dns)
+            .collect::<Vec<&str>>()
+            .join(",")
+    }
+
     pub fn should_renew(&self) -> Result<bool, Error> {
+        self.debug(&format!("Checking for renewal (domains: {})", self.domain_list()));
         if !certificate_files_exists(&self) {
             self.debug("certificate does not exist: requesting one");
             return Ok(true);