なんかもうめっちゃ変えた

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

@@ -0,0 +1,20 @@
+import { PrimaryColumn, Entity, Column } from 'typeorm';
+
+@Entity()
+export class UsedUsername {
+	@PrimaryColumn('varchar', {
+		length: 128,
+	})
+	public username: string;
+
+	@Column('timestamp with time zone')
+	public createdAt: Date;
+
+	constructor(data: Partial<UsedUsername>) {
+		if (data == null) return;
+
+		for (const [k, v] of Object.entries(data)) {
+			(this as any)[k] = v;
+		}
+	}
+}