Call invokes an arbitrary, network-specific procedure call with network-specific
parameters. The guidance for what this endpoint should or could do is
purposely left vague. In Ethereum, this could be used to invoke eth_call
to implement an entire Rosetta API interface for some smart contract that
is not parsed by the implementation creator (like a DEX). This endpoint
could also be used to provide access to data that does not map
to any Rosetta models instead of requiring an integrator to use some
network-specific SDK and call some network-specific endpoint (like surfacing
staking parameters).
Call is NOT a replacement for implementing Rosetta API endpoints or mapping network-specific data to Rosetta models. Rather, it enables developers to build additional Rosetta API interfaces for things they care about without introducing complexity into a base-level Rosetta implementation. Simply put, imagine that the average integrator will use layered Rosetta API implementations that each surfaces unique data.