docs: def rootURL(self, request):
          """
          Return the URL for the root of this website which is appropriate to use
          in links generated in response to the given request.
  
          @type request: L{twisted.web.http.Request}
          @param request: The request which is being responded to.
  
          @rtype: L{URL}
          @return: The location at which the root of the resource hierarchy for
              this website is available.
          """
          host = request.getHeader('host') or self.hostname
          if ':' in host:
              host = host.split(':', 1)[0]
          for domain in [self.hostname] + getDomainNames(self.store):
              if (host == domain or
                  host.startswith('www.') and host[len('www.'):] == domain):
                  return URL(scheme='', netloc='', pathsegs=[''])
          if request.isSecure():
              return self.encryptedRoot(self.hostname)
          else:
              return self.cleartextRoot(self.hostname)