Block reward contract

I’m trying to deploy an ERC-to-native bridge in a test setup with two private chains. This requires a block reward contract which I can’t find an implementation of in the contracts repository. Am I supposed to write it myself? What exactly does it have to do?

What I did find is this interface. However, it differs from the interface defined in the Parity docs. Is it correct that both interfaces need to be implemented?

Deploying of the block reward contract must be part of the network setup process. It is related to the network consensus. Moreover it could be used for different needs not only for the bridge. That’s why the source of this contract is not located in the poa-network-consensus-contracts repo: