add three day grace period

src/utils/subscriptions.ts

@@ -0,0 +1,7 @@
+const GRACE = 60 * 60 * 24 * 3; // 3 days
+
+export function subscriptionValid(subscriptionExpiresTimestamp?: number) {
+    if (!subscriptionExpiresTimestamp) return false;
+
+    return subscriptionExpiresTimestamp + GRACE > Math.ceil(Date.now() / 1000);
+}