cantdown.su developer api

1. upload text paste via curl:
   curl -d "hello world" https://cantdown.su/paste
   curl --data-binary "@file.txt" https://cantdown.su/paste
   curl -F "text=hello world" https://cantdown.su/paste

2. upload file via curl:
   curl -F "file=@image.png" https://cantdown.su/upload

3. custom url / slug:
   curl -H "X-Custom-Url: my-slug" -d "hello world" https://cantdown.su/paste
   curl -H "X-Custom-Url: photo.jpg" -F "file=@photo.png" https://cantdown.su/upload

4. response format:
   by default, returns plain text with the created url and edit link.
   pass "Accept: application/json" header to get JSON output:
   {
     "success": true,
     "url": "https://cantdown.su/abc12345",
     "edit_url": "https://cantdown.su/edit/abc12345?key=...",
     "edit_key": "...",
     "id": "abc12345"
   }