Allow multiple reminder dates for a single chat group

migrations/2024-01-17-093811_multi_ahead_reminders/up.sql

@@ -0,0 +1,13 @@
+-- This migration extracts "remind days ahead" into a separate table so that a chat can configure mutiple reminders
+
+CREATE TABLE reminder (
+   id INTEGER PRIMARY KEY NOT NULL,
+   chat_id INTEGER NOT NULL REFERENCES chat (id) ON DELETE CASCADE,
+   days_ahead BIGINT NOT NULL
+);
+
+CREATE INDEX reminders_chat_id ON reminder (chat_id, days_ahead); -- Having days_ahead as index saves us from taking extra effort for sorted data
+
+INSERT INTO reminder (chat_id, days_ahead) SELECT id, remind_days_ahead FROM chat;
+
+ALTER TABLE chat DROP remind_days_ahead;