Update API urls registration to be lazy and ignore import time errors

mayan/apps/rest_api/classes.py

@@ -1,6 +1,9 @@
 from __future__ import absolute_import
 
 from django.conf.urls import include, patterns, url
+from django.utils.importlib import import_module
+
+from common.utils import load_backend
 
 
 class APIEndPoint(object):
@@ -17,18 +20,18 @@ class APIEndPoint(object):
     def __unicode__(self):
         return unicode(self.name)
 
-    def __init__(self, name):
+    def __init__(self, name, app_name=None):
         self.name = name
         self.endpoints = []
-        self.__class__._registry[name] = self
+        try:
+            api_urls = load_backend('{}.urls.api_urls'.format(app_name or name))
+        except Exception as exception:
+            # Ignore import time errors
+            pass
+        else:
+            self.register_urls(api_urls)
 
-    def add_endpoint(self, view_name, description=None):
-        self.endpoints.append(
-            {
-                'description': description,
-                'view_name': view_name,
-            }
-        )
+        self.__class__._registry[name] = self
 
     def register_urls(self, urlpatterns):
         from .urls import version_0_urlpatterns