Challenger

[imagobea]

• Create a branch from Nightfall Node

• The env var needed is already in place: CHALLENGER_KEY (part of environment). The challenger will only sign transactions from nightfall-optimist/src/services/challenges.mjs so we don't need to set new vars in the app state (like we did for the proposer in nightfall-optimist/src/app.mjs). Instead, read the env var directly from challenges.mjs, and get the address from the private key.

• Where we call .encodeABI(), we need to sign and send the transaction. Please refer to the same implementations in nightfall-optimist/src/routes/proposer.mjs. Please note that you will need a new/different queue.

• In nf3, you can remove pauseQueueChallenger and unpauseQueueChallenger. challengeEnable possibly can stay as it is. For startChallenger, you can follow the approach taken in startProposer, where the emitter was left for compatibility. Even though it does nothing. We can review these changes later.

How do we test these changes is not fully clear. We can test the endpoint with curl (passing api token). We should coordinate with the team to update tests as appropriate.