Force undefined content of category and link to be empty or valid xml

atom.go

@@ -1,6 +1,7 @@
 package atom
 
 import (
+	"encoding/xml"
 	"fmt"
 	"mime"
 	"regexp"
@@ -86,3 +87,9 @@ func isValidLanguageTag(tag LanguageTag) bool {
 func NewURN() IRI {
 	return IRI(fmt.Sprint("urn:uuid:", uuid.New()))
 }
+
+// isValidXML checks whether a string is valid XML. It returns a bool.
+func isValidXML(input string) bool {
+	var v interface{}
+	return xml.Unmarshal([]byte(input), &v) == nil
+}