[C++][RESTSDK] support enums (#2749)

* Support enums

* Updating petstore sample

* Use enum class instead of just enum

* Use string_t for g++ compatibility

* Add enum descriptions

* Fix string parsing. Make g++ compatible.

samples/client/petstore/cpp-restsdk/model/User.cpp

@@ -18,6 +18,9 @@ namespace openapitools {
 namespace client {
 namespace model {
 
+
+
+
 User::User()
 {
     m_Id = 0L;
@@ -412,3 +415,4 @@ void User::unsetUserStatus()
 }
 }
 
+