Implement multisigner for wallet

CHANGELOG.md

@@ -1,3 +1,6 @@
+Development:
+  - upgrade wallet account manager to be able to accept multiple attestations to sign in a single request
+
 0.9.0
   - use go-eth2-client for all beacon node communications
   - beacon block proposal strategy now scales per-node scores based on the distance between the slot and its parent

services/accountmanager/wallet/service.go

@@ -68,6 +68,9 @@ func New(ctx context.Context, params ...Parameter) (*Service, error) {
 		log = log.Level(parameters.logLevel)
 	}
 
+	// Warn about lack of slashing protection
+	log.Warn().Msg("The wallet account manager does not provide built-in slashing protection.  Please use the dirk account manager for production systems.")
+
 	stores := make([]e2wtypes.Store, 0, len(parameters.locations))
 	if len(parameters.locations) == 0 {
 		// Use default location.

services/accountmanager/wallet/validatingaccount.go

@@ -20,6 +20,7 @@ import (
 	eth2client "github.com/attestantio/go-eth2-client"
 	api "github.com/attestantio/go-eth2-client/api/v1"
 	spec "github.com/attestantio/go-eth2-client/spec/phase0"
+	"github.com/attestantio/vouch/services/accountmanager"
 	"github.com/pkg/errors"
 	e2types "github.com/wealdtech/go-eth2-types/v2"
 	e2wtypes "github.com/wealdtech/go-eth2-wallet-types/v2"
@@ -124,6 +125,36 @@ func (d *ValidatingAccount) SignBeaconBlockProposal(ctx context.Context,
 	return d.sign(ctx, messageRoot, domain)
 }
 
+// SignBeaconAttestations signs multiple beacon attestations.
+func (d *ValidatingAccount) SignBeaconAttestations(ctx context.Context,
+	slot spec.Slot,
+	accounts []accountmanager.ValidatingAccount,
+	committeeIndices []spec.CommitteeIndex,
+	blockRoot spec.Root,
+	sourceEpoch spec.Epoch,
+	sourceRoot spec.Root,
+	targetEpoch spec.Epoch,
+	targetRoot spec.Root) ([]spec.BLSSignature, error) {
+
+	signatures := make([]spec.BLSSignature, len(accounts))
+	var err error
+	for i, account := range accounts {
+		signatures[i], err = account.(*ValidatingAccount).SignBeaconAttestation(ctx,
+			slot,
+			committeeIndices[i],
+			blockRoot,
+			sourceEpoch,
+			sourceRoot,
+			targetEpoch,
+			targetRoot)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return signatures, nil
+}
+
 // SignBeaconAttestation signs a beacon attestation item.
 func (d *ValidatingAccount) SignBeaconAttestation(ctx context.Context,
 	slot spec.Slot,