The city of Detroit’s effort to declare some of its general obligation bonds as unsecured debt will be challenged in bankruptcy court Wednesday in what could be a precedent-setting turn in the largest-ever municipal bankruptcy in U.S. history. The issue in front of federal bankruptcy Judge Steven Rhodes is whether a pledge of Detroit tax revenue to pay off the voter-approved bond issues is a binding obligation under Michigan law, as argued by bond insurers in two lawsuits, or merely a promise.