[hw-6] add notifier service, kafka

loms/db/migrations/00004_create_outbox.sql

@@ -0,0 +1,17 @@
+-- +goose Up
+CREATE TABLE if not exists outbox
+(
+    id         bigserial PRIMARY KEY,
+    order_id   BIGINT      NOT NULL,
+    topic      text        NOT NULL,
+    key        text,
+    payload    jsonb       NOT NULL,
+    status     text        NOT NULL DEFAULT 'new', -- new | sent | error
+    created_at timestamptz NOT NULL DEFAULT now(),
+    sent_at    timestamptz
+);
+CREATE INDEX ON outbox (status, created_at);
+
+
+-- +goose Down
+DROP TABLE outbox;