swift-grpc send credentials via ssl - swift

Question

I am trying to work with a gRPC api and I have to send credentials securely. I am having issues to figure this out. I am using the swift-grpc library. I will link the docs and maybe someone can explain what I am supposed to do.
I am still unsure of what makes this secure through ssl(are we sending certificates).
docs from the swift-grpc using tlc library here
If anyone can give an explenation of how the ssl works and what to do that would be great
// code
import Foundation
import GRPC
import NIO
class Networking {
var authServiceClient: PartnerApi2_PartnerApiClient?
let port: Int = 50052
init() {
// build a fountain of EventLoops
let eventLoopGroup = MultiThreadedEventLoopGroup(numberOfThreads: 1)
do {
// open a channel to the gPRC server
let channel = try GRPCChannelPool.with(
target: .host("partner-api.com", port: self.port),
transportSecurity: .plaintext,
eventLoopGroup: eventLoopGroup
)
// create a Client
self.authServiceClient = PartnerApi2_PartnerApiClient.init(channel: channel) //AuthService_AuthServiceRoutesClient(channel: channel)
print("grpc connection initialized")
login(username: "email", password: "password")
} catch {
print("Couldn’t connect to gRPC server")
}
}
func login(username: String, password: String) -> String {
print("Login: username=\(username)")
// build the AccountCredentials object
let accountCredentials: PartnerApi2_AuthenticationRequest = .with {
$0.partnerEmail = username
$0.password = password
}
// grab the login() method from the gRPC client
let call = self.authServiceClient!.authenticate(accountCredentials)
// prepare an empty response object
let oauthCredentials: PartnerApi2_AuthenticationResponse
// execute the gRPC call and grab the result
do {
oauthCredentials = try call.response.wait()
} catch {
print("RPC method ‘login’ failed: \(error)")
// it would be better to throw an error here, but
// let’s keep this simple for demo purposes
return ""
}
// Do something interesting with the result
let oauthToken = oauthCredentials.authToken
print("Logged in with oauth token \(oauthToken)")
// return a value so we can use it in the app
return oauthToken
}
}