Function stored_identifier_membership 

pub async fn stored_identifier_membership(
    conn: &impl DbQuery,
    inbox_id: &str,
    identifier: &Identifier,
) -> Result<Option<bool>, IdentityUpdateError>

identifier_membership for a caller that may make no request, such as an offline build. It reads only the database: the cached state, or one derived from the stored log. A state whose derivation needs a smart contract wallet verdict counts as not holding the identifier.