docs(consensus): describe the attestor committee

docs/guides/external-node/10_attestator_committee.md

@@ -0,0 +1,41 @@
+# Attester Committee
+
+## Overview
+
+Attester committee is a subset of ZKSync nodes. 
+After each l1 batch execution, participating nodes sign its execution result and send back to the network.
+
+The ultimate goal is to make L1 commit operation contingent on such signatures.
+This will improve the security and finality guarantees: 
+having these signatures on L1 shows that additional actors executed the corresponding blocks - 
+and ended up with the same state root hash.
+
+## Current State
+
+Before we start the L1 integration,
+we want to make sure we are able to consistently reach the quorum and collect the signatures in a timely manner. 
+Currently the main node just stores the signatures in the local DB (`l1_batches_consensus` table).
+
+We run a (temporary) PoA network of attesters where the Main Node administrator defines the committee for every L1 batch.
+There is currently no tangible incentive or any kind of actual or implied reward for the participants - we'll be developing them and potential tokenomics later on.
+
+We are looking for participants to this network. 
+
+## Participating in the Attester Committee
+
+Joining the attester committee imposes no additional computational, operational, security, or business overhead for EN operators.
+
+The only difference in behaviour is that the node would asynchronously sign batches and send those signatures to the main node.
+Node checks if its public key is part of the committee for the current l1 batch - if it is, this logic kicks in.
+We expect the participating nodes to have very high uptime, 
+but there are no penalties for not submitting votes (and we wouldn't have any way to impose this).
+
+One can leave the committee any time.
+
+The only action that is required to participate is to share your attester public key with the Main Node operator.
+You can find it in the comment in `consensus_secrets.yaml` file (that was - in most cases - generated by the tool described [here](https://github.com/matter-labs/zksync-era/blob/main/docs/guides/external-node/09_decentralization.md#generating-secrets))
+
+> [!WARNING]
+>
+> Never share your **private** keys. Make sure you are only sharing the **public** key. It looks like this: `# attester:public:secp256k1:02e7b1f24fb58b770cb722bf08e9512c7d8667ec0befa37611eddafd0109656132
+`