[C++] minor improvements (#5319)

* minor code format, make sure cpp samples updated

* add new files

samples/server/petstore/cpp-qt5-qhttpengine-server/.openapi-generator-ignore

@@ -0,0 +1,23 @@
+# OpenAPI Generator Ignore
+# Generated by openapi-generator https://github.com/openapitools/openapi-generator
+
+# Use this file to prevent files from being overwritten by the generator.
+# The patterns follow closely to .gitignore or .dockerignore.
+
+# As an example, the C# client generator defines ApiClient.cs.
+# You can make changes and tell OpenAPI Generator to ignore just this file by uncommenting the following line:
+#ApiClient.cs
+
+# You can match any string of characters against a directory, file or extension with a single asterisk (*):
+#foo/*/qux
+# The above matches foo/bar/qux and foo/baz/qux, but not foo/bar/baz/qux
+
+# You can recursively match patterns against a directory, file or extension with a double asterisk (**):
+#foo/**/qux
+# This matches foo/bar/qux, foo/baz/qux, and foo/bar/baz/qux
+
+# You can also negate patterns with an exclamation (!).
+# For example, you can ignore all files in a docs folder with the file extension .md:
+#docs/*.md
+# Then explicitly reverse the ignore rule for a single file:
+#!docs/README.md

samples/server/petstore/cpp-qt5-qhttpengine-server/.openapi-generator/VERSION

@@ -0,0 +1 @@
+4.3.0-SNAPSHOT

samples/server/petstore/cpp-qt5-qhttpengine-server/server/src/models/OAIHelpers.cpp

@@ -11,6 +11,7 @@
  */
 
 #include <QDebug>
+#include <QJsonParseError>
 #include "OAIHelpers.h"
 
 
@@ -230,6 +231,18 @@ fromStringValue(const QString &inStr, double &value){
     return ok;
 }
 
+bool
+fromStringValue(const QString &inStr, OAIObject &value)
+{
+    QJsonParseError err;
+    QJsonDocument::fromJson(inStr.toUtf8(),&err);
+    if ( err.error == QJsonParseError::NoError ){
+        value.fromJson(inStr);
+        return true;
+    }
+    return false;
+}
+
 bool
 fromStringValue(const QString &inStr, OAIEnum &value){
     value.fromJson(inStr);