Optionally pass in dependencies

[hopeyen]

Problem statement
It is useful to be able to know which dependencies are attached to a given POI attestation. This would help us root cause divergence issues.

Expectation proposal
Imagine an Indexer could pass any number of supported dependencies as configuration. If this were a flag, it could take the form:

--dep <type>:<id>=<uri>

poi-radio --dep postgresql:primary=postgresql://host:5432 --dep chain:mainnet=http://geth:8545

For each provided flag, handler logic could be defined for the type that allows POI Radio to extract the version. For example, for the chain type, the POI radio could call web3_clientVersion at the provided uri to get the client version. A SQL statement could similarly be executed to get PostgreSQL version.

The resulting dependency information could be attached to POI messages.

Alternative considerations

• Utilizes meta field in waku message
• Expose a route on indexer-service/versions