feat: add ability to check if a QGB attestation is in store

proto/celestia/qgb/v1/query.proto

@@ -67,6 +67,12 @@ service Query {
   rpc EVMAddress(QueryEVMAddressRequest) returns (QueryEVMAddressResponse) {
     option (google.api.http).get = "/qgb/v1/evm_address";
   }
+
+  // HasAttestation returns whether the attestation is in store or not.
+  rpc HasAttestation(QueryHasAttestationRequest)
+      returns (QueryHasAttestationResponse) {
+    option (google.api.http).get = "/qgb/v1/has_attestation/{nonce}";
+  }
 }
 
 // QueryParamsRequest
@@ -128,3 +134,9 @@ message QueryEVMAddressRequest { string validator_address = 1; }
 
 // QueryEVMAddressResponse
 message QueryEVMAddressResponse { string evm_address = 1; }
+
+// QueryHasAttestationRequest
+message QueryHasAttestationRequest { uint64 nonce = 1; }
+
+// QueryHasAttestationResponse
+message QueryHasAttestationResponse { bool exists = 1; }

x/qgb/keeper/query_attestation.go

@@ -48,3 +48,16 @@ func (k Keeper) LatestAttestationNonce(
 		Nonce: k.GetLatestAttestationNonce(sdk.UnwrapSDKContext(ctx)),
 	}, nil
 }
+
+func (k Keeper) HasAttestation(
+	ctx context.Context,
+	request *types.QueryHasAttestationRequest,
+) (*types.QueryHasAttestationResponse, error) {
+	_, exists, err := k.GetAttestationByNonce(sdk.UnwrapSDKContext(ctx), request.Nonce)
+	if err != nil {
+		return nil, err
+	}
+	return &types.QueryHasAttestationResponse{
+		Exists: exists,
+	}, nil
+}