Feature request: Traverse callstack

[jonas089]

I would like to request a feature to expand env::caller() by env::nth_caller() or eq.

There are use cases (such as the burn function of a Stablecoin) where I would like to be able to match the immediate caller and depending on the result traverse the callstack further to get the user's account.

Example call stack

User -> Burn Contract -> Stablecoin Contract

If the Burn Contract is the immediate caller of the Stablecoin Contract, then tokens are burned from the Stablecoin Contract's account.

If the immediate caller is anything but the Burn Contract, then I would like to burn from the User's account. Therefore I need to traverse the callstack by n-2, not n-1.

Thanks for considering this feature request.\