PORT ST. LUCIE — The city has put an end to the handsome cash handouts that have buried the municipality deep in debt. The City Council on Monday unanimously restricted borrowing through what’s known as covenant to budget and appropriate bonds. They are bonds for a specific purpose, and have specific guidelines for payback, but in the event of a default, the city assumes the debt. Of the city’s $916 million debt, approximately $335.5 million is from failed or faltering economic-development deals for which the city fronted money with a promise of repayment. Those costly deals include Digital Domain, City Center, Torrey Pines and VGTI. With Digital Domain, the city is stuck repaying $39.9 million, plus interest, it borrowed in 2009 to build the former special-effects company’s Tradition Studios. The company went bankrupt in 2012. With interest, the total owed is $62.9 million.