what about using in edit:

```javascript
_provider = provider;
$scope.provider = _.create(provider);
```
and in save:
```javascript
api.ip.save(_provider, $scope.provider);
```
this should be enough to save changes only so there is no need for deleting any fields and adding it back etc.

maybe we can wrap this into api service - with some `startEdit` method that would use `_.create` and we can pass there only this copy (etag and links are available there).