some improvements to select_query_builder and started insert_query_builder

include/matador/orm/session.hpp

@@ -147,8 +147,6 @@ public:
 private:
   friend class query_select;
 
-  static query::fetchable_query build_select_query(query::select_query_data &&data);
-
 private:
   sql::connection_pool pool_;
   mutable sql::statement_cache cache_;
@@ -321,7 +319,7 @@ utils::result<object::object_ptr<Type>, utils::error> session::find(const Primar
     return utils::failure(make_error(error_code::NoPrimaryKey, "Type hasn't primary key."));
   }
 
-  query::select_query_builder eqb(schema_, *this);
+  query::select_query_builder eqb(schema_);
   const query::table_column c(&it->second.table(), info.primary_key_attribute()->name());
   using namespace matador::query;
   auto data = eqb.build<Type>(c == utils::_);
@@ -352,7 +350,7 @@ utils::result<sql::query_result<Type>, utils::error> session::find(query::criter
     return utils::failure(make_error(error_code::UnknownType, "Failed to determine requested type."));
   }
 
-  query::select_query_builder eqb(schema_, *this);
+  query::select_query_builder eqb(schema_);
   auto data = eqb.build<Type>(std::move(clause));
   if (!data.is_ok()) {
     return utils::failure(make_error(error_code::FailedToBuildQuery,