Allow opting out of persisting instance bans on user delete endpoint

src/api/routes/users/#user_id/delete.ts

@@ -62,7 +62,7 @@ router.post(
 			select: [...PrivateUserProjection, "data"],
 		});
 
-		if (!(await InstanceBan.findOne({ where: { user_id: user.id } })))
+		if ((body?.persistInstanceBan ?? true) && !(await InstanceBan.findOne({ where: { user_id: user.id } })))
 			await InstanceBan.create({ user_id: user.id, reason: body?.reason ?? "<legacy instance ban API - no reason specified>" }).save();
 
 		// prevent bugginess with clients - delete all DMs, only having half of the conversation is quite useless anyhow