Derive param key from admin user class in sessions controller

[Linuus]

Also fixes some minitest warnings and temporarily removes
codeclimate

Fixes #209

@jensljungblad Can you test this? My laptop has some issues so I can't create a new project at the moment.

[Linuus]

@jensljungblad I just did a manual test for this and it worked fine. I also updated the changelog.

Can we write a good test for this somehow? It's a bit annoying because I guess we'd have to have another dummy app...

[jensljungblad]

@Linuus Depends on if we need an integration test or not. If we do, I think a separate sessions_controller would be enough. Something like

class SessionsControllerWithAnotherAdminUser < ApplicationController
  include Godmin::Authentication::SessionsController
  include Godmin::Authentication

  def admin_user_class
    AnotherAdminUser
  end
end

And then a separate route. But I think maybe its enough with something that tests the admin_user_params function? Then we could just create a sessions controller class in the test and instantiate it?

[Linuus]

@jensljungblad That's true. I'll see what I can come up with.

[Linuus]

@jensljungblad Pushed a test for this now.

Merge?

EDIT: They are failing in Rails < 5 because they changed syntax in the tests.

[Linuus]

Ok, tests updated again. I'm using the old style now, without the params: keyword. This still works in Rails 5 but prints a deprecation warning.

[jensljungblad]

Other than the fact that our integration test setup is beginning to feel a bit ridiculous (which has nothing to do with this PR) it looks good to me!

[jensljungblad]

(We did some weird workaround for another function that changed between Rails 4 and 5, but perhaps we should get back to this once Rails 5.1 is released)