Remove the reliance a reference to the Controller to get the link that a
subscription is tied to by explicitly handling the SubscriptionRequest
and passing the link to the SubscriptionController.
Notify the SubscriptionController that a connection closed from the
Connection instead of having the subscription controller set up an event
to do so. This simplifies the logic on the SubscriptionController's
side.
Structure the storage of mods on the controller into into a reusable
component in preparation for the host using the same kind of mod storage
to retrieve and cache the mods it needs to run mod packs on instances.
Load hosts, instances, mod packs, mods and users before constructing the
Controller instances. This allows these resources to be correctly typed
as always available and prevents any possibility of save being initiated
on these resources before they are loaded.