Fault-tolerant delivery system

migrations/20250901135528_create_idempotency_table.sql

@@ -0,0 +1,14 @@
+CREATE TYPE header_pair AS (
+    name TEXT,
+    value BYTEA
+);
+
+CREATE TABLE idempotency (
+    user_id UUID NOT NULL REFERENCES users (user_id),
+    idempotency_key TEXT NOT NULL,
+    response_status_code SMALLINT NOT NULL,
+    response_headers header_pair[] NOT NULL,
+    response_body BYTEA NOT NULL,
+    created_at TIMESTAMPTZ NOT NULL,
+    PRIMARY KEY (user_id, idempotency_key)
+);