Whether Hercules CI is installed on this account as an App.
An account that does not have an installation can not be
properly accessed by Hercules, but may be visible nonetheless
at times because of OAuth scopes.
As an example, non-installed accounts show up when a GitHub
user signs in for the first time via OAuth, until they decide
to install it on their GitHub user. Another example is GitHub
organizations that don't have an installation yet.