A post on r/sustainability is reminding people that beat-up sandals do not always need to be replaced. In the Reddit post, before-and-after photos show a worn pair of Birkenstock Arizona sandals was repaired with a new suede footbed, a fresh sole, and sealed cork, all while the original leather straps and structure stayed in place. "A good pair of shoes shouldn't end up in a landfill because the sole wore out," wrote the original poster, who own…