NewClient creates an *http.Client from a Context and TicketSource.

ReuseTicketSource returns a TicketSource which repeatedly returns the same ticket as long as it's valid, starting with t.

HTTPClient is the context key to use with golang.org/x/net/context's WithValue function to associate an *http.Client value with a context.

Ticket represents the crendentials used to authorize the requests to access protected resources on the PVE server.

Transport is an http.RoundTripper that makes OAuth 2.0 HTTP requests, wrapping a base RoundTripper and adding an Authorization header with a ticket from the supplied Sources.

A TicketSource is anything that can return a ticket.