URI-encoding when redirecting legacy URLs to /content

Testing of this functionality revealed that the query part containing +
symbols (as replacement for spaces in the parameter values) isn't
forwarded properly as the + symbols are URI-encoded (this is a bug on
the part of the `RequestContext::get_query()` the result of which
already contains URI-encoded +'s).

src/server/internalServer.cpp

@@ -607,7 +607,7 @@ std::unique_ptr<Response> InternalServer::handle_request(const RequestContext& r
     if (isEndpointUrl(url, "catch"))
       return handle_catch(request);
 
-    std::string contentUrl = m_root + "/content" + url;
+    std::string contentUrl = urlEncode(m_root + "/content" + url);
     const std::string query = request.get_query();
     if ( ! query.empty() )
       contentUrl += "?" + query;