get Contact By User Name And Domain
fun getContactByUserNameAndDomain(userName: String, domain: String, onCompletion: (Either<Contact, SippoResourceError>) -> Unit)
Retrieves a contact by their userName and associated domain.
Parameters
user Name
The userName of the contact to retrieve.
domain
The domain associated with the contact.
on Completion
Callback that will be invoked when the request is completed. It will receive the contact in case of success or a SippoResourceError otherwise.