Add a new field to the alert schema to fix a mismatch between the prior schema and the upstream NWS API

internal/sinks/postgres/doc.go

@@ -198,6 +198,7 @@
 //     - sent TIMESTAMPTZ NULL -> payload.alerts[i].sent
 //     - effective TIMESTAMPTZ NULL -> payload.alerts[i].effective
 //     - onset TIMESTAMPTZ NULL -> payload.alerts[i].onset
+//     - ends TIMESTAMPTZ NULL -> payload.alerts[i].ends
 //     - expires TIMESTAMPTZ NULL -> payload.alerts[i].expires
 //     - area_description TEXT NULL -> payload.alerts[i].areaDescription
 //     - sender_name TEXT NULL -> payload.alerts[i].senderName