Server sets userlang cookie as global and permanent

Without specifying the "Path" attribute of the cookie in the "Set-Cookie" header
we end up with multiple instances of the cookie for different URLs. We
want a single "global" cookie for kiwix-serve. Besides we want it to be
"permanent" rather than a session cookie, hence the large (1-year-long)
TTL value for the "Max-Age" attribute.

src/server/request_context.cpp

@@ -68,12 +68,13 @@ fullURL2LocalURL(const std::string& full_url, const std::string& rootLocation)
 } // unnamed namespace
 
 RequestContext::RequestContext(struct MHD_Connection* connection,
-                               std::string rootLocation,
+                               std::string _rootLocation,
                                const std::string& _url,
                                const std::string& _method,
                                const std::string& version) :
+  rootLocation(_rootLocation),
   full_url(_url),
-  url(fullURL2LocalURL(_url, rootLocation)),
+  url(fullURL2LocalURL(_url, _rootLocation)),
   method(str2RequestMethod(_method)),
   version(version),
   requestIndex(s_requestIndex++),
@@ -193,6 +194,10 @@ std::string RequestContext::get_full_url() const {
   return full_url;
 }
 
+std::string RequestContext::get_root_path() const {
+  return rootLocation.empty() ? "/" : rootLocation;
+}
+
 bool RequestContext::is_valid_url() const {
   return !url.empty();
 }

src/server/request_context.h

@@ -91,6 +91,7 @@ class RequestContext {
     std::string get_url() const;
     std::string get_url_part(int part) const;
     std::string get_full_url() const;
+    std::string get_root_path() const;
 
     std::string get_query() const { return queryString; }
 
@@ -136,6 +137,7 @@ class RequestContext {
     };
 
   private: // data
+    std::string rootLocation;
     std::string full_url;
     std::string url;
     RequestMethod method;

src/server/response.cpp

@@ -388,7 +388,9 @@ MHD_Result Response::send(const RequestContext& request, MHD_Connection* connect
   }
 
   if ( ! request.user_language_comes_from_cookie() ) {
-    const std::string cookie = "userlang=" + request.get_user_language();
+    const std::string cookie = "userlang=" + request.get_user_language()
+                               + ";Path=" + request.get_root_path()
+                               + ";Max-Age=31536000";
     MHD_add_response_header(response, MHD_HTTP_HEADER_SET_COOKIE, cookie.c_str());
   }