Assemble takes a slice and inserts the tail into the onion of the head until there is no tail left.

Encode is the generic encoder for an onion, all onions can be encoded with it.

Codec is a unit of data that can be read and written from a binary form.

Ngin is the generic interface for onion encoders to access the engine without tying the dependencies together.

Onion are messages that can be layered over each other and have a set of processing instructions for the data in them, and, if relevant, how to account for them in sessions.