code: @Nonnull
    public DigestAuthServerBuilder addDomain (@Nonnull final ISimpleURL aURL)
    {
      ValueEnforcer.notNull (aURL, "Url");
  
      final String sURL = aURL.getAsStringWithEncodedParameters ();
      // Check for spaces, as all URLs are concatenated with spaces!
      if (sURL.indexOf (' ') >= 0)
        throw new IllegalArgumentException ("URL may not contain spaces: '" + sURL + "'");
      m_aDomains.add (sURL);
      return this;
    }
docs: Add an URIs, as specified in RFC XURI, that define the protection space. If
  a URI is an abs_path, it is relative to the canonical root URL of the
  server being accessed. An absoluteURI in this list may refer to a different
  server than the one being accessed. The client can use this list to
  determine the set of URIs for which the same authentication information may
  be sent: any URI that has a URI in this list as a prefix (after both have
  been made absolute) may be assumed to be in the same protection space. If
  this directive is omitted or its value is empty, the client should assume
  that the protection space consists of all URIs on the responding server.
  This directive is not meaningful in Proxy-Authenticate headers, for which
  the protection space is always the entire proxy; if present it should be
  ignored.
  
  @param aURL
  The absolute or relative path which is protected. May not be
  <code>null</code>.
  @return this