if err != nil {
		return err
	}
	for k, v := range ret {
		if !strings.EqualFold(k, "authorization") {
			if _, ok := dst[k]; ok {
				return fmt.Errorf("underlying %s credentials contain a %s header which is already present in the combined credentials", kind, k)
			}
			dst[k] = v
		} else {
			dst[dstHdr] = v
		}
	}
	return nil
}

type hubMembership struct {
	WorkloadIdentityPool string
}