Fix group usage permission

[AlexHTW]

So, originally I just wanted to add the admin list to the loop that checks if an allowed user is in the group (first commit).
But then discovered a bug in is_user_in_group, it only checks the first user of the allowed user list (in all my previous testing, I never put myself in a different position until I tested the addition of the admin list 🙈)
The current implementation of is_user_in_group raises an error if the first allowed user is not in the group and doesn't continue with the other users.
My fix is using the context (now that I think about it, maybe it would work with the previous implementation as well, if the error would be caught), so I added it to is_allowed and is_within_budget.
I gotta say, I am a bit out of my depth with the best practices of the telegram library. But for my tests it all seems to be at least functional now.

[dkvdm]

ayyy, that works! much better, and clean implementation 👍
happy that we got to the bottom of this 🙂