Add support for CAA record type

src/base/charstr.rs

@@ -380,6 +380,22 @@ impl<Octs: AsRef<[u8]> + ?Sized> CharStr<Octs> {
             .compose(target)?;
         target.append_slice(self.0.as_ref())
     }
+
+    /// Appends the canonical wire format representation to an octets builder.
+    pub fn compose_canonical<Target: OctetsBuilder + ?Sized>(
+        &self,
+        target: &mut Target,
+    ) -> Result<(), Target::AppendError> {
+        u8::try_from(self.0.as_ref().len())
+            .expect("long charstr")
+            .compose(target)?;
+
+        for ch in self.0.as_ref() {
+            ch.compose(target)?;
+        }
+
+        Ok(())
+    }
 }
 
 impl<Octs> CharStr<Octs> {

src/base/zonefile_fmt.rs

@@ -371,4 +371,18 @@ mod test {
             record.display_zonefile(false).to_string()
         );
     }
+
+    #[test]
+    fn caa_record() {
+        use crate::rdata::Caa;
+        let record = create_record(Caa::new(
+            0,
+            "issue".parse().unwrap(),
+            "ca.example.net".as_bytes().to_vec(),
+        ));
+        assert_eq!(
+            "example.com. 3600 IN CAA 0 issue \"ca.example.net\"",
+            record.display_zonefile(false).to_string()
+        );
+    }
 }