send certificate notifications in 21, 14, 7 days

db/patch-notification_sent_history.sql

@@ -0,0 +1,18 @@
+-- You should not modify if this have pushed to Github, unless it does serious wrong with the db.
+BEGIN TRANSACTION;
+
+CREATE TABLE [notification_sent_history] (
+    [id] INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
+    [type] VARCHAR(50) NOT NULL,
+    [monitor_id] INTEGER NOT NULL,
+    [days] INTEGER NOT NULL,
+    UNIQUE([type], [monitor_id], [days])
+);
+
+CREATE INDEX [good_index] ON [notification_sent_history] (
+    [type],
+    [monitor_id],
+    [days]
+);
+
+COMMIT;