Is trimming the beard obligatory, and what is the meaning of the Hadith: "The Messenger of Allah used to trim his beard from its length and breadth"?

The aforementioned Hadith is weak and not authentically attributed to the Messenger of Allah, may Allah bless him and grant him peace. The one accused of fabricating it is Umar ibn Harun al-Balkhi, who is considered a liar and abandoned by the imams of Hadith.