UserData is not saved after processing deferred unsubscriptions during `FetchExternalUpdatesAsync`

[lethal-guitar]

If deferred unsubscriptions are removed during FetchExternalUpdatesAsync, user data will not be saved after calling RemoveDeferredUnsubscription. This causes the SDK to process the same deferred unsubscription again every time it is initialized, unless user data is saved due to another reason.

I ran into this while I was testing network error handling. I performed an unsubscribe operation in my game's UI after disabling the internet connection. Afterwards, every time I would open my game's mod browser, the SDK would process the same deferred unsubscription every time.
I noticed this while investigating #19.

There should either be a call to SaveUserDataToStorageAsync after the following loop (probably conditional on any deferred unsubscriptions having been removed):

modio-sdk/modio/modio/detail/ops/FetchExternalUpdates.h

Line 45 in dd3147e

while (Modio::Detail::SDKSessionData::HasDeferredUnsubscriptions())

Or alternatively, UnsubscribeFromModAsync should call RemoveDeferredUnsubscription before it saves the user data:

modio-sdk/modio/modio/detail/ops/UnsubscribeFromMod.h

Line 97 in dd3147e

Modio::Detail::SDKSessionData::InvalidateSubscriptionCache();

[stephenwhittle]

Both of these related issues landed while we were in the middle of preparing the 2026.8 release, but they've been ticketed internally and should be addressed in 2026.9

[lethal-guitar]

@stephenwhittle great, thanks!