なんかもうめっちゃ変えた

packages/backend/src/models/entities/AnnouncementRead.ts

@@ -0,0 +1,36 @@
+import { PrimaryColumn, Entity, Index, JoinColumn, Column, ManyToOne } from 'typeorm';
+import { id } from '../id.js';
+import { User } from './User.js';
+import { Announcement } from './Announcement.js';
+
+@Entity()
+@Index(['userId', 'announcementId'], { unique: true })
+export class AnnouncementRead {
+	@PrimaryColumn(id())
+	public id: string;
+
+	@Column('timestamp with time zone', {
+		comment: 'The created date of the AnnouncementRead.',
+	})
+	public createdAt: Date;
+
+	@Index()
+	@Column(id())
+	public userId: User['id'];
+
+	@ManyToOne(type => User, {
+		onDelete: 'CASCADE',
+	})
+	@JoinColumn()
+	public user: User | null;
+
+	@Index()
+	@Column(id())
+	public announcementId: Announcement['id'];
+
+	@ManyToOne(type => Announcement, {
+		onDelete: 'CASCADE',
+	})
+	@JoinColumn()
+	public announcement: Announcement | null;
+}