```ruby
GDS::SSO.config do |config|
  config.user_model = "User"
  config.oauth_id = ENV["OAUTH_ID"] || "abcdefg"
  config.oauth_secret = ENV["OAUTH_SECRET"] || "secret"
  config.oauth_root_url = Plek.find("signon")
end
```

Use external_url_for when configuring GDS::SSO
user
```ruby
GDS::SSO.config do |config|
  config.user_model = "User"
  config.oauth_id = ENV["OAUTH_ID"] || "abcdefg"
  config.oauth_secret = ENV["OAUTH_SECRET"] || "secret"
  config.oauth_root_url = Plek.new.external_url_for("signon")
end
```
assistant