Add support for multidb with Django (Closes #171).

The ``factory.django.DjangoModelFactory`` now takes an extra option:

```
class MyFactory(factory.django.DjangoModelFactory):
    class Meta:
        model = models.MyModel
        database = 'replica'
```

This will create all instances of ``models.Model`` in the ``'replica'``
database.

3 files changed, 19 insertions, 0 deletions

diff --git a/tests/djapp/settings.py b/tests/djapp/settings.py
index c051faf..18e43dd 100644
--- a/tests/djapp/settings.py
+++ b/tests/djapp/settings.py
@@ -34,6 +34,9 @@ DATABASES = {
     'default': {
         'ENGINE': 'django.db.backends.sqlite3',
     },
+    'replica': {
+        'ENGINE': 'django.db.backends.sqlite3',
+    },
 }
 
 
diff --git a/tests/test_django.py b/tests/test_django.py
index 4653305..a8f1f77 100644
--- a/tests/test_django.py
+++ b/tests/test_django.py
@@ -165,6 +165,16 @@ class ModelTests(django_test.TestCase):
 
         self.assertRaises(factory.FactoryError, UnsetModelFactory.create)
 
+    def test_cross_database(self):
+        class OtherDBFactory(factory.django.DjangoModelFactory):
+            class Meta:
+                model = models.StandardModel
+                database = 'replica'
+
+        obj = OtherDBFactory()
+        self.assertFalse(models.StandardModel.objects.exists())
+        self.assertEqual(obj, models.StandardModel.objects.using('replica').get())
+
 
 @unittest.skipIf(django is None, "Django not installed.")
 class DjangoPkSequenceTestCase(django_test.TestCase):
diff --git a/tests/test_using.py b/tests/test_using.py
index 7318f2e..1d7977f 100644
--- a/tests/test_using.py
+++ b/tests/test_using.py
@@ -69,6 +69,9 @@ class FakeModel(object):
         def order_by(self, *args, **kwargs):
             return [1]
 
+        def using(self, db):
+            return self
+
     objects = FakeModelManager()
 
     def __init__(self, **kwargs):
@@ -1490,6 +1493,9 @@ class BetterFakeModelManager(object):
         instance.id = 2
         return instance, True
 
+    def using(self, db):
+        return self
+
 
 class BetterFakeModel(object):
     @classmethod