This is so that new channel types added by Discord (that may or may not
support the features we need for proxying to work) don't throw piles of
error codes at users when they try to proxy.
- remove Cluster.User
- remove Cluster.Application (it was only being used as an alternative to Cluster.User for some reason)
- move Bot.PermissionsIn to DiscordCacheExtensions
This happened because we cache Task instances, not the values, and a failed task is still a *valid* task that can repeatedly be awaited. This lead to the Task being saved even if it failed, and the same exception constantly being re-thrown.
This fix invalidates the cache if it finds a failed Task, and lets it retry fetching as normal (hopefully successfully this time).
This also refactors a large portion of the DI toolchain, since
I discovered that you shouldn't be reusing IDbConnection objects.
Instead, most services and stores are now declared transient, and
the webhook cache has been moved to a database-independent storage
singleton by itself.
