add an endpoint for home site (post login)

[matthewandrews]

We need an endpoint called something like /homesite which does something like this:

@SSO
def homesite() {
  redirect(grailsApplication.config.getValue('userdetails.homesite.url', String, 'https://www.ala.org.au/'))
}

... so that the Login button on the static home site can have a URL like https://auth.ala.org.au/userdetails/homesite which would then take the user back to the static home page after login.