docs: public void addHeader(String name, String value) {
          if (name == null || name.trim().length() == 0) {
              throw new IllegalArgumentException("The header name must not be null or empty.");
          }
  
          if (value == null) {
              throw new IllegalArgumentException("The header value must not be null.");
          }
  
          this.headers.put(name, value);
      }