All parties to a joint obligation, including negotiable paper, copartnership debts, and all contracts upon which they are liable jointly, shall be severally liable also for the full amount thereof. They may be sued thereon jointly, or separate actions may be brought against each or any of them, and judgment rendered in each, without barring an action against any of those not included in such judgment, or releasing any of those not sued. The court, upon its own motion or on application of any interested party, may require the plaintiff to bring in as defendants all the parties jointly liable on the obligation in suit.