example of adding othername SAN to a CSR?

[learningSwif]

Hi,
In my csr, i'd like to be able to include a UPN value for the SAN. In openssl's configuration, this would appear in the following form: subjectAltName = otherName:1.3.18.0.2.4.318;UTF8:test@example.com
I see CertificateRequestBuilder() accepts 'otherName' as a parameter, but since i'm new to swift, I'm not sure how to create the proper data for that parameter. Can anyone provide an example that shows how to accomplish this?
Just for reference, this is an example that i'm starting from

let csr =
try CertificationRequest.Builder()
.subject(name: NameBuilder().add("Outfox Signing", forTypeName: "CN").name)
.alternativeNames(names: .otherName(???HOW TO POPULATE THIS???))
.publicKey(keyPair: Self.keyPair, usage: [.keyEncipherment])
.extendedKeyUsage(keyPurposes: [kp.clientAuth.oid, kp.serverAuth.oid], isCritical: true)
.build(signingKey: Self.keyPair.privateKey, digestAlgorithm: .sha256)

output(csr)

Thanks!