Add picture field to facebook User struct

* Add the Facebook user's picture to the User struct
since it requires no additional permissions and is
often used in login flows

Docs: https://developers.facebook.com/docs/graph-api/overview

facebook/verify.go

@@ -12,9 +12,14 @@ const facebookAPI = "https://graph.facebook.com/v2.9/"
 //
 // Note that user ids are unique to each app.
 type User struct {
-	ID    string `json:"id"`
-	Name  string `json:"name"`
-	Email string `json:"email"`
+	ID      string `json:"id"`
+	Name    string `json:"name"`
+	Email   string `json:"email"`
+	Picture struct {
+		Data struct {
+			URL string `json:"url"`
+		} `json:"data"`
+	} `json:"picture"`
 }
 
 // client is a Facebook client for obtaining the current User.
@@ -36,6 +41,6 @@ func (c *client) Me() (*User, *http.Response, error) {
 	// Facebook returns JSON as Content-Type text/javascript :(
 	// Set Accept header to receive proper Content-Type application/json
 	// so Sling will decode into the struct
-	resp, err := c.sling.New().Set("Accept", "application/json").Get("me?fields=name,email").ReceiveSuccess(user)
+	resp, err := c.sling.New().Set("Accept", "application/json").Get("me?fields=name,email,picture").ReceiveSuccess(user)
 	return user, resp, err
 }