Telebot, how knowing the ID to make a link to the user?

Question

Python

I am making a telegram bot, a la a store where you can register a purchase, or order some kind of service, in general, just to make it easier.
I am writing as an education, purely for myself.
I can't figure out how to make it so that if the user clicks the "order" button, then the bot sends the "admin" not an id, but a link to the user, knowing his id, so that after that he can write to this user himself?

Answer 1

I found a solution through "mem = message.from_user.username", it returns the username, if not, then None.
As I understand it, making a link to a contact (t.me/...) of a person is not possible if he does not have a username, so this will probably be the only solution
I did:
bot.send_message(***id_admin** *,
f'Customer made a purchase!\n'
f'Customer: @{mem}\n'
f'Choice: {last_take_buy[-1]}',
)