Add payload attestation validator duty (#9178)

Co-Authored-By: Eitan Seri-Levi <eserilev@ucsc.edu>

Co-Authored-By: Jimmy Chen <jchen.tc@gmail.com>

validator_client/validator_store/src/lib.rs

@@ -7,10 +7,11 @@ use std::future::Future;
 use std::sync::Arc;
 use types::{
     Address, Attestation, AttestationError, BlindedBeaconBlock, Epoch, EthSpec,
-    ExecutionPayloadEnvelope, Graffiti, Hash256, SelectionProof, SignedAggregateAndProof,
-    SignedBlindedBeaconBlock, SignedContributionAndProof, SignedExecutionPayloadEnvelope,
-    SignedValidatorRegistrationData, Slot, SyncCommitteeContribution, SyncCommitteeMessage,
-    SyncSelectionProof, SyncSubnetId, ValidatorRegistrationData,
+    ExecutionPayloadEnvelope, Graffiti, Hash256, PayloadAttestationData, PayloadAttestationMessage,
+    SelectionProof, SignedAggregateAndProof, SignedBlindedBeaconBlock, SignedContributionAndProof,
+    SignedExecutionPayloadEnvelope, SignedValidatorRegistrationData, Slot,
+    SyncCommitteeContribution, SyncCommitteeMessage, SyncSelectionProof, SyncSubnetId,
+    ValidatorRegistrationData,
 };
 
 #[derive(Debug, PartialEq, Clone)]
@@ -205,6 +206,13 @@ pub trait ValidatorStore: Send + Sync {
         envelope: ExecutionPayloadEnvelope<Self::E>,
     ) -> impl Future<Output = Result<SignedExecutionPayloadEnvelope<Self::E>, Error<Self::Error>>> + Send;
 
+    /// Sign a `PayloadAttestationData` for the PTC.
+    fn sign_payload_attestation(
+        &self,
+        validator_pubkey: PublicKeyBytes,
+        data: PayloadAttestationData,
+    ) -> impl Future<Output = Result<PayloadAttestationMessage, Error<Self::Error>>> + Send;
+
     /// Returns `ProposalData` for the provided `pubkey` if it exists in `InitializedValidators`.
     /// `ProposalData` fields include defaulting logic described in `get_fee_recipient_defaulting`,
     /// `get_gas_limit_defaulting`, and `get_builder_proposals_defaulting`.