A boxing legend is born. This week, the trailer debuted for the new documentary "Cassius X: Becoming Ali", which tells the story of the man who would become Muhammad Ali. [readmore label="READ MORE: " link="https://etcanada.com/news/855374/muhammad-ali-80th-birthday-to-be-marked-with-virtual-event/" /] Focusing on the early years of his life and career, the documentary tracks Ali, back when he was known…