Destination contract and source / from contract allow listing

[drinkcoffee]

Function call approaches should have the ability to switch on an "allow" or "white" listing of contracts that can call the system or be called by the system. A possible approach would be:

Have a bool destContractAllowListingEnabled
and have a mapping(address => bool) destContractAllowed

By default when the contract is constructed destContractAllowListingEnabled is false. When one or more contracts are added to the allow list, destContractAllowListingEnabled would be set to true.

The ability to remove allowed contracts is required too.