Returns an upload link for a folder. POST the file(s) to this link (see Upload file).

• Requires upload permission on the folder p.
• With replace=1 the returned link already contains ?replace=1 (existing files are overwritten); in that case append further query parameters with &, e.g. &ret-json=1. replace is ignored for folders with a custom share permission.
• The link can be used several times until the token expires.