Default file-based OAuth token storage.
Tokens are written as JSON to
~/.longbridge/openapi/tokens/<client_id> — matching the path
used by the Rust and Go SDKs.
This is the storage used by Longbridge.OAuth when no custom
storage: option is passed.
Summary
Functions
Returns the on-disk path that this storage uses for a given
client_id. Mirrors Longbridge.OAuth.token_path/1.