Reapply "feat(loyalty): EnakPoint & EnakCoin" (#32)

This reverts commit 4e24f9bbb0.

migrations/000097_create_wallet_expiry_reminders.up.sql

@@ -0,0 +1,11 @@
+-- Which expiry reminders have gone out (docs/prd-point-coin.md F12): one per
+-- customer, currency and expiry day. The row is written before the push is sent, so
+-- several instances of the job, or a restart, never remind twice.
+CREATE TABLE wallet_expiry_reminders (
+    customer_id UUID NOT NULL REFERENCES customers(id) ON DELETE CASCADE,
+    currency VARCHAR(10) NOT NULL CHECK (currency IN ('POINT','COIN')),
+    expiry_date DATE NOT NULL,
+    amount BIGINT NOT NULL,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    PRIMARY KEY (customer_id, currency, expiry_date)
+);