When Post Malone announced his intention to cross over to country earlier this year, he took everyone by surprise, as a guy who began his career as a rapper. But the shift didn’t come entirely out of the blue. The Grapevine artist, whose driver’s license reads “Austin Richard Post,” has long been interested in genre bending and has incorporated country elements into his work as far back as “Go Flex” from his 2016 debut, Stoney. That album also teased Post’s superpower: his ability to work with a wide array of artists from across the spectrum of popular music. Stoney featured appearances from Justin Bieber, Kehlani, Quavo, and 2 Chainz; on his official country debut, F-1 Trillion (out August 16), fifteen of the eighteen tracks involve guest artists, ranging from current megastars such as Chris Stapleton and…