Refactor rest_api app and the method end points are registered. All apps API URL endpoints are now registered under the 'rest_api' namespace.

Update DRF and DRF swagger versions. Update all apps API registration method.

mayan/apps/user_management/apps.py

@@ -28,7 +28,7 @@ class UserManagementApp(MayanAppConfig):
     def ready(self):
         super(UserManagementApp, self).ready()
 
-        APIEndPoint('users', app_name='user_management')
+        APIEndPoint(app=self, version_string='1')
 
         MetadataLookup(description=_('All the groups.'), name='group', value=Group.objects.all())
         MetadataLookup(description=_('All the users.'), name='users', value=get_user_model().objects.all())