Rihanna celebrates Fenty x Puma spring '18 at Coachella. CREDIT: Rex Shutterstock Leave it to Rihanna to rock thigh-high Uggs at Coachella. "Extra af #chella," the singer-turned-designer captioned her first post Sunday featuring her head-to-toe Y/Project look, including outrageous stiletto boots in collaboration with Ugg for fall '18. The snap was from the night...