AddHeader creates the given set of headers if needed, and then adds the given header:.

AddValue creates the given set of query parameters if needed, an then adds the given parameter.

CopyHeader creates a copy of the given set of headers.

CopyQuery creates a copy of the given set of query parameters.

CopyValues copies a slice of strings.

SetDeadline creates the given context, if needed, and sets the given deadline.

SetTimeout creates the given context, if needed, and sets the given timeout.

TokenResponse is used to unmarshal the sub-set of properties JSON token responses that we need.