All judgments in this state shall bear interest upon the principal amount recovered at the rate of 12 percent per year unless the judgment is rendered on a written contract or obligation providing for interest at a specified rate, in which case the judgment shall bear interest at the rate specified in such contract or obligation. The postjudgment interest provided for in this Code section shall apply automatically to all judgments in this state and such interest shall be collectable as a part of each such judgment whether or not such judgment specifically reflects the entitlement to such interest.