Calculate the next date using periodicity strategies.

All these strategies encapsulate how the Carbon library adds the
interval to the current date.

Monthly, Quarterly, Half-Yearly, and Yearly explicitly use the
overflow control to guarantee the end of the next month or year
adequately.

app/Support/Calendar/Periodicity.php

@@ -0,0 +1,33 @@
+<?php
+
+/**
+ * Copyright (c) 2023 james@firefly-iii.org
+ *
+ * This file is part of Firefly III (https://github.com/firefly-iii).
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+namespace FireflyIII\Support\Calendar;
+
+enum Periodicity
+{
+    case Daily;
+    case Weekly;
+    case Fortnightly;
+    case Monthly;
+    case Quarterly;
+    case HalfYearly;
+    case Yearly;
+}