My question asks if it is possible to use Telegram's API to communicate with someone in a way that does not require the user to create or authenticate with an account. But it may require a loosely permissive authorization token provided by the person with whom the user wishes to communicate.
Intergram achieves this (if I understand correctly) by using an intermediary server between the user and Telegram's API.
What I'm further asking is if the same behavior is possible without the intermediary server.