oauth cleanup: test fakes and generic provider

app/controllers/auth_controller.rb

@@ -10,11 +10,11 @@ class AuthController < ApplicationController
   end
 
   def auth
-    redirect_to client.auth_code.authorize_url(redirect_uri: ENV['gitlab_callback'])
+    redirect_to client.auth_code.authorize_url(redirect_uri: ENV['callback_url'])
   end
 
   def callback
-    access_token = client.auth_code.get_token(params[:code], redirect_uri: ENV['gitlab_callback'])
+    access_token = client.auth_code.get_token(params[:code], redirect_uri: ENV['callback_url'])
     session[:token] = access_token.token
     user_info(access_token)
 
@@ -24,7 +24,7 @@ class AuthController < ApplicationController
   private
 
     def user_info access_token
-      @user_info ||= JSON.parse(access_token.get(ENV['gitlab_oauth'] + '/api/v3/user').body)
+      @user_info ||= JSON.parse(access_token.get(ENV['oauth_path'] + '/api/v3/user').body)
       session[:name] = @user_info['name']
       session[:avatar] = @user_info['avatar_url']
       session[:admin] = @user_info['is_admin']
@@ -32,9 +32,9 @@ class AuthController < ApplicationController
 
     def client
       OAuth2::Client.new(
-        ENV['gitlab_client'],
-        ENV['gitlab_secret'],
-        site: ENV['gitlab_oauth']
+        ENV['client_key'],
+        ENV['secret_key'],
+        site: ENV['oauth_path']
       )
     end
 end

app/views/auth/login.erb

@@ -1 +1 @@
-<%= link_to "Authenticate with gitlab", auth_path %>
+<%= link_to "Authenticate with #{ENV['oauth_provider']}", auth_path %>