User language control via userlang query param

This is a draft commit enabling the testing of the support for
kiwix-serve internationalization.

test/server.cpp

@@ -1182,6 +1182,17 @@ R"EXPECTEDRESPONSE([
     //EOLWHITESPACEMARKER
   }
 ]
+)EXPECTEDRESPONSE"
+    },
+    { /* url: */ "/ROOT/suggest?content=zimfile&term=abracadabra&userlang=hy",
+R"EXPECTEDRESPONSE([
+  {
+    "value" : "abracadabra ",
+    "label" : "որոնել 'abracadabra'...",
+    "kind" : "pattern"
+    //EOLWHITESPACEMARKER
+  }
+]
 )EXPECTEDRESPONSE"
     },
   };