A Mayor Bill de Blasio donor-turned-felon testified in extraordinary detail Thursday that he and his businessman pals wrote the book on city corruption — buying off the Mayor’s Office and the Police Department using brazen pay-to-play tactics. “We’re going to become significant contributors, but we want access,” Jona Rechnitz, 34, testified telling de Blasio fundraiser Ross Offinger after Hizzoner clinched the Democratic nod for mayor in 2013. De Blasio soon paid Rechnitz a visit in his office, the disgraced businessman told jurors in Manhattan federal court. De Blasio — who last year called his relationship with Rechnitz “not a particularly...