Usage of ValidatorIndex inside Bolt Sidecar

[merklefruit]

Our current API definitions for constraints contain the validatorIndex of the validator that is opted-in to Bolt and has signed that specific preconfirmation request.

This means that we have to deal with this when generating the constraints, which happens inside Bolt sidecar.
Right now, this value is set to 0 always here: https://github.com/chainbound/bolt/pull/53/files#diff-709413e7867c3101338b843ff608b31b209deb676433b25160302d6819deafffR124

This issue is to keep track of this dangling data point and to brainstorm solutions. Some questions:

• should bolt sidecar work with >1 validators connected? if so, how do we figure out which validator to sign commitments with
• are there DDoS attacks that benefit from knowing the validatorIndex bound to some bolt sidecar?

[merklefruit]

An acceptable solution for now will be to specify validator indexes via the CLI.

we should add a validator_index cli parameter that can be a comma-delimited array of numbers (e.g. called via --validator-index 2,3,4,5,9) or an array to indicate contiguous indexes (e.g. --validator-index [2,9].