def refresh_token!(refresh_token)
      old_token = OAuth2::AccessToken.new(oauth_client,'', refresh_token: refresh_token)
      self.access_token = old_token.refresh!
    end
def refresh_token!(refresh_token)
      old_token = OAuth2::AccessToken.new(oauth_client,'', refresh_token: refresh_token)
      self.access_token = old_token.refresh!
    end
=begin rdoc
OAuth refresh_token method

Refresh tokens when token was expired

== Params:

* refresh_token - refresh_token in last got #access_token
=end