CREATE TABLE "Notification" (
	"id" int,
	"sender_id" int,
	"recipient_id" int,
	"object_id" int,
	"object_type" varchar(255),
	"is_read" bool,
	"date_created" datetime,
	FOREIGN KEY("sender_id") REFERENCES "User" ("id")
);
CREATE TABLE "User" (
	"id" int,
	"username" varchar(255)
);