support 'user_id' in addition to 'id' and 'ID' for service identifier

packages/rocketchat-custom-oauth/custom_oauth_server.coffee

@@ -103,6 +103,10 @@ class CustomOAuth
 			if identity?.ID and not identity.id
 				identity.id = identity.ID
 
+			# Fix Auth0-like identities having 'user_id' instead of 'id'
+			if identity?.user_id and not identity.id
+				identity.id = identity.user_id
+
 			console.log 'id:', JSON.stringify identity, null, '  '
 
 			serviceData =