IDP Hinting reloaded
Simplest point: parameter will be named idphint, not idp.
Spec is currently rewritten here:https://docs.google.com/document/d/1IcbEJDrnoUqLtC4L5LPoAWbuRsULsqXrUMOk7yzlRNk/edit#
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information