As an authenticated user, I would like to know that information I share is not public

[nathanhilbert]

• Check granular permissions for forum
• Write unit test for authentication
• clean up permissions with decorators as in https://github.com/USStateDept/FPA_Core/blob/master/openspending/auth/forum.py#L15

[nathanhilbert]

@dstepp currently the /forums url is accessible to anonymous users. They will see the categories and topic discussions. If the user tries to click on a topic they get a 403 error. I think if the user is anonymous, they should see the forums at the top nav, but they would see a page saying that if they are government they can log in or sign up.