We seem to be using this idiom in a growing number of places in the query codebase:

const auto isInternalClient = !opCtx->getClient()->session() ||
        (opCtx->getClient()->session()->getTags() & transport::Session::kInternalClient);

It would be nice to have a helper Client::isInternal().

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In addition to introducing the helper function, existing code that explicitly checks the `kInternalClient` flag should use the new helper function when possible.