before_filter that checks for a login token and logs the user in if it's valid

maybe_login_from_token.rb

def maybe_login_from_token
  Rails.logger.info "maybe_login_from_token: '#{ params[:token] }'"
  return if (token = params[:token]).blank?

  if (user = User.find_by_token(token))
    Rails.logger.info "One time login token used for user #{ user.id }"
    sign_in(user)
  else
    Rails.logger.info "No user found from token: '#{ token }'"
  end

  # strip token regardless of success
  redirect_to request.path,
              params.except(:token, :action, :controller)
end