Nest subscription and key resource under /list

• Nest subscription resource under /lists and pass the list email to the controller methods. The subscriptions email is not a unique identifier since there can be multiple with the same email address, so we always need the list context to identify the subscription.
• Nest key resource under /lists
• Use the list_id in the URI instead of passing it as a query param for the send_list_key_to_subscription route
• Remove unsued methods from api daemon helper

part of #383 (closed)