code: private void getStringFromValue(final StringBuilder builder, final String directive, final String value) {
          if (value != null) {
              builder.append(directive).append(" ").append(value).append(";");
          }
      }
docs: Assists in the formatting of a single CSP directive.
  @param builder a StringBuilder object
  @param directive a CSP directive
  @param value the value of the CSP directive