code: public String encryptPropertyValue(String propertyValue) {
          byte[] bytes = cryptex.encryptString(key, propertyValue);
          String encryptedValue = Base64Utils.encode(bytes);
          return ENCRYPTED_NOTATION + encryptedValue;
      }
docs: This method encrypts a property value in such a way that it can be placed in a properties
  file and automatically decrypted using this placeholder configurer.
  
  @param propertyValue The property value to be encrypted.
  @return The encrypted property value.