added belongs to and has one tests

test/backends/SessionInsertHasOne.cpp

@@ -0,0 +1,22 @@
+#include "catch2/catch_test_macros.hpp"
+
+#include "SessionFixture.hpp"
+
+#include "connection.hpp"
+
+#include "matador/query/session.hpp"
+
+#include "models/user.hpp"
+
+using namespace matador::test;
+using namespace matador::query;
+using namespace matador::object;
+
+TEST_CASE_METHOD(SessionFixture, "Test insert object with has_one relation", "[session][insert][has_one]") {
+  session sess{conn};
+  user_pk_generator u;
+  u.name = "John Doe";
+  sess.persist(u);
+
+  REQUIRE(u.id > 0);
+}