Southampton have completed the signing of Rangers midfielder Joe Aribo on a four-year contract.   The 25-year-old Nigeria international joins for a fee reported to be about £6m, rising to £10m with add-ons.     Aribo spent three seasons at Ibrox after moving from Charlton in 2019, helping Rangers win the Scottish Premiership in 2021 and scoring in last season's Europa League final defeat.   "It's an amazing club with a lot of history here," Aribo said.   "The Premier League is the best league in the world. I've been watching it since I was a young boy. It's