Hi. Thanks for the PR, nice idea 👍
Looking at the code base, I see that we already have the properties

• User.name
• User.full_name
• Chat.full_name

and your PR basically copies User.name and Chat.full_name to SharedUser.
To avoid too much duplication, I would like you instead introduce a new module telegram._utils.usernames whith two function get_name and get_full_name. They would both accept a object of type

class UserLike(typing.Protocol):
    first_name: typing.Optional[str]
    last_name: typing.Optional[str]
    username: typing.Optional[str]

Would that be doable for you?

Note that you can copy the tests from test_chat/test_user. I'd like to avoid introducing unittest into our test suite b/c we use nowhere else.

Closing in favor of #4713