Where is this year’s song of the summer?It’s the question that’s haunted road trippers and pool partiers for months now. But like so many low-stakes mysteries, the answer has been hiding in plain sight (or, in this case, earshot) all along.If we’re going with cold, hard facts — Billboard chart data — there’s one song that’s dominated the airwaves as the weather has warmed. It’s just that a soaring love ballad a 24-year-old TikToker wrote…