Even geniuses need day jobs: Vivaldi, for example, got a gig as the music master at an orphanage for girls in Venice. And, in a Hollywood plot-twist, he promptly transformed its orchestra and choir of “unwanteds” into one of the most highly desirable ensembles in all of Europe. His only surviving oratorio for those remarkable female artists is Juditha Triumphans (Judith Triumphant), a dramatic retelling of the Biblical story of Judith’s seduction and beheading of the Assyrian general Holofernes. Now Boston Baroque brings this rarely heard gem back to Jordan Hall. Mezzo-soprano Daniela Mack makes her Boston Baroque debut and favorites soprano Amanda Forsythe and mezzo-soprano Leah Wool return to the stage for a one-night only performance.