This method is only called when the request matches
a route to a resource.
Parameters:
req – Request object that will be passed to the
routed responder.
resp – Response object that will be passed to the
responder.
resource – Resource object to which the request was
routed.
params – A dict-like object representing any additional
params derived from the route’s URI template fields,
that will be passed to the resource’s responder
method as keyword arguments.