Allow developer to know if a record is read/only or read/write

In your interface you want to hide some actions if the record is readonly but Kinto.js doesn't expose that.
You could use `client.api` to fetch the permission but if you want to be offline first you need to know it while being offline.

A nice api would be to have a flag telling you if you can edit or not the record you are currently working with.

At the moment, if you want to manage permissions you can only do it online using `client.api`. Does it make sense to enable that offline too? Even if we don't offer offline modification, we could still offer a flag to see if the object is editable.

Big thanks to all my contributors to this issue. It was awesome folks, keep rocking it!

Bisous,
Adrian

Start by reading the client.api permission-fetching flow and the offline record behavior described in the issue. Define how an offline record exposes whether it is editable, including the stated case where offline modification is not offered, and verify that the result lets an interface hide or show actions without an online request.

Written by the indexing model from the issue text.