Thx @kobaltz for your answer,
I tried adding the following in `application.rb` but it did not solve the problem for google_oauth2 hybrid auth:
```
config.session_store :cookie_store, key: '_interslice_session', domain: 'localhost'
```
However, as I found a 'workaround' with `provider_ignores_state: Rails.env.development?`, I am now more bothered with the facebook auth problem... :-/