“The Federal Magistrates Act, 28 U.S.C. § 631, permits district courts to assign designated functions to magistrate judges. For example, magistrate judges are authorized to: issue order concerning release or detention of persons pending trial; take acknowledgments, affidavits, and depositions; and enter sentences for petty offenses. § 636(a). They also may hear and determine, when designated to do so, any pretrial matter pending before the district court, with the exception of certain specified motions. Magistrate judges may also conduct hearings and propose recommendations for those motions, applications for post-trial criminal relief, and conditions of confinement petitions. § 636(b)(1). If the parties consent, they may conduct misdemeanor criminal trials and civil trials. §§ 636(a)(3) and (c)(1).” J. Kennedy, Gonzalez v. United States, 553 U.S. 242, 245 (2008).