introduced field_attributes shortcuts and added method on_base() to all processor classes

include/matador/sql/internal/object_result_binder.hpp

@@ -27,6 +27,8 @@ public:
     binder_ = nullptr;
   }
 
+  template<typename BaseType>
+  static void on_base(const BaseType&) {}
   template<typename ValueType>
   void on_primary_key(const char *id, ValueType &value, const utils::primary_key_attribute& attr);
   static void on_revision(const char * /*id*/, uint64_t &/*rev*/) {}
@@ -73,6 +75,8 @@ public:
 
   void reset();
 
+  template<typename BaseType>
+  static void on_base(const BaseType&) {}
   template < class Type >
   void on_primary_key(const char *id, Type &val, const utils::primary_key_attribute& attr) {
     utils::data_type_traits<Type>::read_value(*binder_, id, index_++, val, attr.size());