update VC to use SingleAttestation (#6884)

Author: tersec

beacon_chain/spec/eth2_apis/eth2_rest_serialization.nim

@@ -378,7 +378,7 @@ type
 
   EncodeArrays* =
     seq[phase0.Attestation] |
-    seq[electra.Attestation] |
+    seq[electra.SingleAttestation] |
     seq[PrepareBeaconProposer] |
     seq[RemoteKeystoreInfo] |
     seq[RestCommitteeSubscription] |

beacon_chain/spec/forks.nim

@@ -178,7 +178,7 @@ type
 
   ForkyAttestation* =
     phase0.Attestation |
-    electra.Attestation
+    electra.SingleAttestation
 
   ForkedAttestation* = object
     case kind*: ConsensusFork
@@ -461,6 +461,7 @@ template kind*(
       electra.MsgTrustedSignedBeaconBlock |
       electra.TrustedSignedBeaconBlock |
       electra.Attestation |
+      electra.SingleAttestation |
       electra.AggregateAndProof |
       electra.SignedAggregateAndProof |
       electra_mev.SignedBlindedBeaconBlock]): ConsensusFork =

beacon_chain/validator_client/attestation_service.nim

@@ -1,5 +1,5 @@
 # beacon_chain
-# Copyright (c) 2021-2024 Status Research & Development GmbH
+# Copyright (c) 2021-2025 Status Research & Development GmbH
 # Licensed and distributed under either of
 #   * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
 #   * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
@@ -72,10 +72,12 @@ proc serveAttestation(
     logScope:
       attestation = shortLog(atst)
     try:
-      when atst is electra.Attestation:
+      when atst is electra.SingleAttestation:
         await vc.submitPoolAttestationsV2(@[atst], ApiStrategyKind.First)
-      else:
+      elif atst is phase0.Attestation:
         await vc.submitPoolAttestations(@[atst], ApiStrategyKind.First)
+      else:
+        static: doAssert false
     except ValidatorApiError as exc:
       warn "Unable to publish attestation", reason = exc.getFailureReason()
       return false
@@ -85,7 +87,7 @@ proc serveAttestation(
 
   let res =
     if afterElectra:
-      let attestation = registered.toElectraAttestation(signature)
+      let attestation = registered.toSingleAttestation(signature)
       submitAttestation(attestation)
     else:
       let attestation = registered.toAttestation(signature)