migrate db to support confirmation emails

migrations/20240226143929_add_status_to_subscriptions.sql

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+ALTER TABLE subscriptions ADD COLUMN status TEXT NULL;

migrations/20240226144038_make_status_not_null_in_subscriptions.sql

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+BEGIN;
+    -- Backfill `status` for historical entries
+    UPDATE subscriptions
+        SET status = 'confirmed'
+        WHERE status IS NULL;
+    -- Make `status` mandatory
+    ALTER TABLE subscriptions ALTER COLUMN status SET NOT NULL;
+COMMIT;

migrations/20240226144122_create_subscription_tokens_table.sql

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+CREATE TABLE subscription_tokens(
+   subscription_token TEXT NOT NULL,
+   subscriber_id uuid NOT NULL
+      REFERENCES subscriptions (id),
+   PRIMARY KEY (subscription_token)
+);