Auth client

Auth client package is used to identify a thing and authorize a thing's access to a channel.

To identify a thing, you need a valid thing key. You retrieve thing's identity in the form of a thing ID. The latter is used in CRUD operations on things and their connections.

To authorize a thing's access to a channel, you need a valid thing ID and a valid channel ID. If a thing is not connected to a channel, the auth client responds with an error. Otherwise, a nil value is returned, signaling the successful authorization.