Shared capability not specified for `opfs` and `mini_moka`

[QazCetelic]

Related to #7826

[dosubot]

Hi @QazCetelic! I'm Dosu and I'm helping the Apache OpenDAL team.

Looking at the code, here's what I found for these two services:

mini_moka — Its capability declaration does not explicitly set shared [1]. It relies on ..Default::default(), which means shared defaults to false. This is likely correct (it's an in-memory cache like moka, which explicitly sets shared: false [2]), but it should be made explicit for clarity.

opfs — The OPFS backend is currently a stub that returns a default AccessorInfo with all capabilities at their default values [3]. It doesn't declare any capabilities explicitly, so shared is also implicitly false. Whether OPFS should be shared: true or false depends on the intended usage — the Origin Private File System is per-origin and browser-specific, so shared: false seems appropriate, but it should still be declared explicitly.

For reference, the shared capability indicates whether an operator supports shared/concurrent access [4]. The convention in other services is to explicitly set it — true for network/filesystem backends (S3, FS, Azure Blob) and false for in-memory caches (Memory, Moka).

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