Add front-end link to (dummy) group list page.

src/client_front_end.cpp

@@ -180,6 +180,15 @@ static void load_log_file(stringstream& out_ss) {
              , ostreambuf_iterator<char>(out_ss));
 }
 
+void ClientFrontEnd::handle_group_list( const Request&
+                                      , Response& res
+                                      , std::stringstream& ss)
+{
+    res.set(http::field::content_type, "text/plain");
+
+    ss << "TODO\n";
+}
+
 void ClientFrontEnd::handle_portal( ClientConfig& config
                                   , const Request& req, Response& res, stringstream& ss
                                   , cache::Client* cache_client
@@ -316,6 +325,8 @@ void ClientFrontEnd::handle_portal( ClientConfig& config
                               " (i.e. not older than %s).<br>\n")
               % max_age.total_seconds() % past_as_string(max_age));
 
+        ss << "<a href=\"" << group_list_apath << "\">See announced groups</a><br>\n";
+
         Cancel cancel;
         sys::error_code ec;
         auto local_size = cache_client->local_size(cancel, yield[ec]);
@@ -451,6 +462,8 @@ Response ClientFrontEnd::serve( ClientConfig& config
     } else if (path == "/logfile.txt") {
         res.set(http::field::content_type, "text/plain");
         load_log_file(ss);
+    } else if (path == group_list_apath) {
+        handle_group_list(req, res, ss);
     } else if (path == "/api/status") {
         sys::error_code e;
         handle_status( config, udp_port, upnps, reachability

src/client_front_end.h

@@ -34,6 +34,11 @@ class ClientFrontEnd {
         = boost::intrusive::list_base_hook
             <boost::intrusive::link_mode
                 <boost::intrusive::auto_unlink>>;
+
+public:
+    // Absolute paths of allowed URLs.
+    inline static const std::string group_list_apath = "/groups.txt";
+
 public:
     using Request = http::request<http::string_body>;
     using Response = http::response<http::dynamic_body>;
@@ -95,6 +100,10 @@ private:
     void handle_ca_pem( const Request&, Response&, std::stringstream&
                       , const CACertificate& );
 
+    void handle_group_list( const Request&
+                          , Response&
+                          , std::stringstream&);
+
     void handle_portal( ClientConfig&
                       , const Request&
                       , Response&