Save API failing to work because it strips the double-slash

[anjackson]

Requests like

https://beta.webarchive.org.uk/save/https%3A%2F%2F%2Fwww.bl.uk%2Fbritishlibrary%2F~%2Fmedia%2Fbl%2Fglobal%2Fabout%2520us%2Ffreedom%2520of%2520information%2Fpublication%2520scheme%2F4%2520decisions%2Fboard%2520meetings%2Fboard%2520meetings%25202018%2F180227-368%2Fblb%25201803.pdf

get response like

{
  "result": {
    "ia": {
      "event": "save-page-now",
      "reason": "OK",
      "status": 200
    },
    "ukwa": {
      "event": "save-page-now",
      "reason": "Crawl Requested",
      "status": 201
    }
  },
  "url": "https:/www.bl.uk/britishlibrary/~/media/bl/global/about%20us/freedom%20of%20information/publication%20scheme/4%20decisions/board%20meetings/board%20meetings%202018/180227-368/blb%201803.pdf"
}

i.e. https:/www. so something is stripping the slashes.