CREATE TABLE "notification_kinds" (    "id" SERIAL PRIMARY KEY,    "name" VARCHAR NOT NULL); CREATE UNIQUE INDEX "index_notification_kinds_on_name" ON "notification_kinds" ("name"); CREATE TABLE notifications (    "id" SERIAL PRIMARY KEY,    "created_at" TIMESTAMP NOT NULL DEFAULT now(),    "recipient_id" INTEGER NOT NULL REFERENCES users (id) ON DELETE CASCADE,    "kind" INTEGER NOT NULL REFERENCES notification_kinds (id),    "entity_id" INTEGER,    "content" TEXT,    "is_read" BOOLEAN NOT NULL DEFAULT FALSE,    "response" BOOLEAN); CREATE INDEX    "index_notifications_on_recipient_id_is_read_kind_entity_id"    ON "notifications"    ("recipient_id", "is_read", "kind", "entity_id");