chore: synchronize code and database schema (#8577)

* chore: remove default null

null is always the default value if a table column is nullable, and typeorm's
@Column only accepts strings for default.

* chore: synchronize code with database schema

* chore: sync generated migrations with code

packages/backend/src/models/entities/auth-session.ts

@@ -23,7 +23,7 @@ export class AuthSession {
 		...id(),
 		nullable: true,
 	})
-	public userId: User['id'];
+	public userId: User['id'] | null;
 
 	@ManyToOne(type => User, {
 		onDelete: 'CASCADE',