It was always going to be a case of ‘when’ rather than ‘if’ in terms of Johnny Sexton signing a contract extension that takes him through to the 2023 World Cup. When the news came through yesterday that he had put pen to paper, the most noteworthy part of the news was not that the deal was done, but that Sexton confirmed that the tournament would be the end point for his career. Still, he had plenty to say when asked about what will now be his last 18 months or so as a professional athlete. “I’ve always invested in myself, in that I’ve always done stuff outside of the Leinster set-up or the Irish set-up at home, or meeting new people and investing in that, researching things. There’s lots of good p …