So far we only allowed calls to the Contributors contract from the
Operator. With the new registry concept we can call functions again
directly on the Contributors contract (without the need to call it through
the operator).
This changes the authentication for the contributor management functions
to allow either core contributors or the operator to call them.
In the future I envision a bit more flexible and configurable
authentication concept that can more easily evolve over time.
This allows use to call the methods with a string but still store the
name as bytes32.
I also had some issues when calling the methods from ethers.js and a
string parameter so this is easier and safer.
