Added child_enpoints_model example.

As per https://github.com/GoogleCloudPlatform/endpoints-proto-datastore/issues/110#issuecomment-60832527 I have added the example for simple parent child relationship.
I will need parent ID for later MyModel calls, so yes, I want ID in there.

On Tue Oct 28 2014 at 6:54:07 PM Danny Hermes <notifications@github.com>
wrote:

> In examples/child_endpoints_model/main.py:
>
> > +  parent_model_class = MyParent
> > +
> > +  attr1 = ndb.StringProperty()
> > +  attr2 = ndb.StringProperty()
> > +  created = ndb.DateTimeProperty(auto_now_add=True)
> > +  modified_by = ndb.UserProperty(required=True)
> > +
> > +
> > +@endpoints.api(name='myapi', version='v1', description='My Little API')
> > +class MyApi(remote.Service):
> > +
> > +  # This method is not defined in any of the previous examples; it allows a
> > +  # parent entity to be inserted so that it can be used as an ancestor. Since
> > +  # the ProtoRPC message schema for MyParent is a single field "name", this will
> > +  # be all that is contained in the request and the response.
> > +  @MyParent.method(path='myparent', http_method='POST',
>
> You might want to specify request_fields=('name',) here unless you are OK
> with id in the request.
>
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> <https://github.com/GoogleCloudPlatform/endpoints-proto-datastore/pull/112/files#r19516370>
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