Add isNullOrEmpty() utility method to StringUtils

Author: intisy

src/main/java/io/github/intisy/utils/core/StringUtils.java

@@ -227,4 +227,14 @@ public static String toTitleCase(String input) {
 
         return titleCase.toString().trim();
     }
+
+    /**
+     * Checks if a string is null or empty.
+     *
+     * @param str the string to check
+     * @return true if the string is null or empty, false otherwise
+     */
+    public static boolean isNullOrEmpty(String str) {
+        return str == null || str.isEmpty();
+    }
 }