Fix extra string actions

internal/clipboard/service.go

@@ -45,6 +45,22 @@ func (s Service) Copy(model vault.Model, entryID string, target Target) error {
 	return nil
 }
 
+func (s Service) CopyCustomField(model vault.Model, entryID, key string) error {
+	entry, err := findEntry(model, entryID)
+	if err != nil {
+		return err
+	}
+
+	content, ok := entry.Fields[key]
+	if !ok {
+		return ErrUnsupportedTarget
+	}
+	if err := s.writer().WriteText(content); err != nil {
+		return writeError{err: err}
+	}
+	return nil
+}
+
 func (s Service) writer() Writer {
 	if s.Writer != nil {
 		return s.Writer