Support Mem-only durability for sync

[sync-by-unito]

Core config has a durability setting:

    enum class Durability : uint16_t {
        Full,
        MemOnly,
        Async ///< Not yet supported on windows.
    };

Use different durability setting to open the same Realm file will cause a core crash:

Durability setting (as passed to the SharedGroup constructor) was not consistent across the session

But sync client is always open Realm file with Durability::Full. That prevents bindings to give user the option to use MemOnly which is allowed for non-sync Realm.

Is it a restriction from sync or a bug?

related java issue: realm/realm-java#4957

---

The problem is that when sync is enabled, one cannot use "mem only" durability setting when opening Realm files, because that conflicts with the default durability setting used by the sync client. Realm requires that all participants of a file access session uses the same durability setting.

Support for using "mem only" durability inside sync client could easily be implemented.

[sync-by-unito]

➤ Jonathan Reams commented:

This was fixed in #4839