update linkedin example (#507)

demo/oauth2-linkedin.r

@@ -2,7 +2,7 @@ library(httr)
 
 # 1. Find OAuth settings for linkedin:
 # https://developer.linkedin.com/documents/linkedins-oauth-details
-oauth_endpoints("linkedin")
+endpoints <- oauth_endpoints("linkedin")
 
 # 2. Register an application at https://www.linkedin.com/secure/developer
 # Make sure to register http://localhost:1410/ as an "OAuth 2.0 Redirect URL".
@@ -14,29 +14,7 @@ myapp <- oauth_app("linkedin",
  secret = "n7vBr3lokGOCDKCd")
 
 # 3. Get OAuth credentials
-# LinkedIn doesn't implement OAuth 2.0 standard
-# (http://tools.ietf.org/html/rfc6750#section-2) so we extend the Token2.0
-# ref class to implement a custom sign method.
-TokenLinkedIn <- R6::R6Class("TokenLinkedIn", inherit = Token2.0, list(
- sign = function(method, url) {
- url <- parse_url(url)
- url$query$oauth2_access_token <- self$credentials$access_token
- request(url = build_url(url))
- },
- can_refresh = function() {
- TRUE
- },
- refresh = function() {
- self$credentials <- init_oauth2.0(self$endpoint, self$app,
- scope = self$params$scope, type = self$params$type,
- use_oob = self$params$use_oob)
- }
-))
-token <- TokenLinkedIn$new(
- endpoint = oauth_endpoints("linkedin"),
- app = myapp,
- params = list(use_oob = FALSE, scope = NULL, type = NULL)
-)
+token <- oauth2.0_token(endpoints, myapp)
 
 # 4. Use API
 req <- GET("https://api.linkedin.com/v1/people/~", config(token = token))