Fix #130 - Validate IP format in session

   . Add a new IPAddressField type.
   . Update IP type from CharField to IPAddressField.
   . Add a new Session factory test to know if a session can be instanciated.
   . Add 2 session tests (IP valid  & IP not valid test).

Author: philippe VESSIERE

ban/tests/auth/test_session.py

@@ -37,7 +37,7 @@ def test_session_can_be_created_with_a_client_and_an_valid_IPAddress():
     assert session.ip == '192.168.0.1'
 
 
-def test_session_can_not_be_created_with_a_client_and_an_unvalid_IPAddress():
+def test_session_can_not_be_created_with_a_client_and_an_invalid_IPAddress():
     client = ClientFactory()
     with pytest.raises(ValueError):
         models.Session.create(client=client, ip='999.999.999.999')
@@ -49,7 +49,7 @@ def test_session_can_be_created_with_a_user_and_an_valid_IPAddress():
     assert session.ip == '192.168.0.1'
 
 
-def test_session_can_not_be_created_with_a_user_and_an_unvalid_IPAddress():
+def test_session_can_not_be_created_with_a_user_and_an_invalid_IPAddress():
     user = UserFactory()
     with pytest.raises(ValueError):
         models.Session.create(user=user, ip='999.999.999.999')