Set OmniAuth full_host parameter to ensure redirect URIs are correct

Closes #1967

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
 v 7.14.0 (unreleased)
+  - Set OmniAuth full_host parameter to ensure redirect URIs are correct (Stan Hu)
   - Expire Rails cache entries after two weeks to prevent endless Redis growth
   - Add support for destroying project milestones (Stan Hu)
 

config/initializers/7_omniauth.rb

@@ -11,6 +11,7 @@ if Gitlab::LDAP::Config.enabled?
   end
 end
 
+OmniAuth.config.full_host = Settings.gitlab['url']
 OmniAuth.config.allowed_request_methods = [:post]
 #In case of auto sign-in, the GET method is used (users don't get to click on a button)
 OmniAuth.config.allowed_request_methods << :get if Gitlab.config.omniauth.auto_sign_in_with_provider.present?