[Discord] LobbyMemberTransactions are structs and need to be handled as value types

Discord's LobbyMemberTransactions are structs and need to be handled as value types. This is causing lobby or member change operations to fail as they are not being properly stored before being flushed. This is causing LockFailed errors to be fired when a lobby member has been edited more than once in a update tick.

The flushing of changes should also be encouraged and better documented.