REFACTOR: Initialize auth providers after plugin.activate!

Also added some helpful functionality for plugin developers:
- Raises RuntimeException if the auth provider has been registered too late
- Logs use of deprecated parameters

lib/middleware/omniauth_bypass_middleware.rb

@@ -7,6 +7,8 @@ class Middleware::OmniauthBypassMiddleware
   def initialize(app, options = {})
     @app = app
 
+    Discourse.plugins.each(&:notify_before_auth)
+
     # if you need to test this and are having ssl issues see:
     #  http://stackoverflow.com/questions/6756460/openssl-error-using-omniauth-specified-ssl-path-but-didnt-work
     # OpenSSL::SSL::VERIFY_PEER = OpenSSL::SSL::VERIFY_NONE if Rails.env.development?