This tennis superstar is a trendsetter and a go-getter. In an exclusive story with Good Morning America, fast-food salad chain Sweetgreen announced its newest partnership with four-time Grand Slam champion Naomi Osaka, making her both the first national athlete ambassador for the company and its youngest investor. “Naomi represents not only a great tennis player, but so much beyond that. She stands up for what she believes in — a lot of social justice issues — and is really into speaking to this next generation in a way that still has humility and is connected to culture,” Sweetgreen co-founder Nathaniel Ru — also chief brand officer — told the outlet. “She just really aligns with our values at Sweetgreen and is passionate about it.” In her new role, Osaka hopes to use her image and influence to change the way both brands and athletes advise on nutrition for the general public. “Anyone that knows me knows I’ve been into @sweetgreen for a while (I eat it minimum three times a week...