added support for Model migrations

now we have a table core.migration and each model (User, Group, Item, ItemContent and a new Migration) have its own
row in the table with a version number

added to config:
db_make_migration_if_needed and db_stop_if_migration_fails (need description yet)

winixd/models/group.cpp

@@ -0,0 +1,81 @@
+/*
+ * This file is a part of Winix
+ * and is distributed under the 2-Clause BSD licence.
+ * Author: Tomasz Sowa <t.sowa@ttmath.org>
+ */
+
+/*
+ * Copyright (c) 2021, Tomasz Sowa
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "group.h"
+
+
+namespace Winix
+{
+
+
+bool Group::do_migration(int & current_table_version)
+{
+	bool ok = true;
+
+	ok = ok && morm::Model::do_migration(current_table_version, 1, this, &Group::do_migration_to_1);
+	ok = ok && morm::Model::do_migration(current_table_version, 2, this, &Group::do_migration_to_2);
+
+	return ok;
+}
+
+
+bool Group::do_migration_to_1()
+{
+	const char * str = R"sql(
+		CREATE TABLE core."group" (
+			id serial,
+			"group" character varying(20)
+		);
+	)sql";
+
+	db_query(str);
+	return true;
+}
+
+
+bool Group::do_migration_to_2()
+{
+	const char * str = R"sql(
+		alter table core.group rename column "group" to "name";
+	)sql";
+
+	return db_query(str);
+}
+
+
+
+
+}
+
+