Correctly escape strings if needed and check for it

category.go

@@ -3,6 +3,7 @@ package atomfeed
 import (
 	"errors"
 	"fmt"
+	"html"
 )
 
 type Category struct {
@@ -22,6 +23,10 @@ func NewCategory(term string) (*Category, error) {
 	return &Category{Term: term, Content: content}, nil
 }
 
+func (c *Category) SetLabel(label string) {
+	c.Label = html.UnescapeString(label)
+}
+
 func (c *Category) Check() error {
 	if c.Term == "" {
 		return errors.New("term attribute of category empty")
@@ -33,6 +38,10 @@ func (c *Category) Check() error {
 		}
 	}
 
+	if !isCorrectlyEscaped(c.Label) {
+		return fmt.Errorf("label attribute of category %v not correctly escaped", c.Label)
+	}
+
 	if c.Content == nil {
 		return errors.New("no content element of category")
 	} else {