rfq: oracle rpc accept group keys

The public oracle server RPC endpoints for querying prices would only
accept a specifier that sets only the asset ID. We may now accept group
keys as well, so we consider any specifier to be valid. This is needed
as we're later going to create a oracle rpc server harness to test out
this code path.

Author: GeorgeTsagk

rfq/oracle.go

@@ -195,21 +195,8 @@ func (r *RpcPriceOracle) QueryAskPrice(ctx context.Context,
 	assetRateHint fn.Option[rfqmsg.AssetRate]) (*OracleResponse,
 	error) {
 
-	// For now, we only support querying the ask price with an asset ID.
-	if !assetSpecifier.HasId() {
-		return nil, fmt.Errorf("asset ID is nil")
-	}
-
-	var (
-		subjectAssetId = make([]byte, 32)
-		paymentAssetId = make([]byte, 32)
-	)
-
-	// The payment asset ID is BTC, so we leave it at all zeroes. We only
-	// set the subject asset ID.
-	assetSpecifier.WhenId(func(assetId asset.ID) {
-		copy(subjectAssetId, assetId[:])
-	})
+	// The payment asset ID is BTC, so we leave it at all zeroes.
+	var paymentAssetId = make([]byte, 32)
 
 	// Marshal asset max amount.
 	assetMaxAmount := assetMaxAmt.UnwrapOr(0)
@@ -228,12 +215,8 @@ func (r *RpcPriceOracle) QueryAskPrice(ctx context.Context,
 	)
 
 	req := &oraclerpc.QueryAssetRatesRequest{
-		TransactionType: oraclerpc.TransactionType_SALE,
-		SubjectAsset: &oraclerpc.AssetSpecifier{
-			Id: &oraclerpc.AssetSpecifier_AssetId{
-				AssetId: subjectAssetId,
-			},
-		},
+		TransactionType:       oraclerpc.TransactionType_SALE,
+		SubjectAsset:          rpcMarshalAssetSpecifier(assetSpecifier),
 		SubjectAssetMaxAmount: assetMaxAmount,
 		PaymentAsset: &oraclerpc.AssetSpecifier{
 			Id: &oraclerpc.AssetSpecifier_AssetId{
@@ -303,21 +286,8 @@ func (r *RpcPriceOracle) QueryBidPrice(ctx context.Context,
 	assetRateHint fn.Option[rfqmsg.AssetRate]) (*OracleResponse,
 	error) {
 
-	// For now, we only support querying the ask price with an asset ID.
-	if !assetSpecifier.HasId() {
-		return nil, fmt.Errorf("asset ID is nil")
-	}
-
-	var (
-		subjectAssetId = make([]byte, 32)
-		paymentAssetId = make([]byte, 32)
-	)
-
-	// The payment asset ID is BTC, so we leave it at all zeroes. We only
-	// set the subject asset ID.
-	assetSpecifier.WhenId(func(assetId asset.ID) {
-		copy(subjectAssetId, assetId[:])
-	})
+	// The payment asset ID is BTC, so we leave it at all zeroes.
+	var paymentAssetId = make([]byte, 32)
 
 	// Marshal asset max amount.
 	assetMaxAmount := assetMaxAmt.UnwrapOr(0)
@@ -336,12 +306,8 @@ func (r *RpcPriceOracle) QueryBidPrice(ctx context.Context,
 	}
 
 	req := &oraclerpc.QueryAssetRatesRequest{
-		TransactionType: oraclerpc.TransactionType_PURCHASE,
-		SubjectAsset: &oraclerpc.AssetSpecifier{
-			Id: &oraclerpc.AssetSpecifier_AssetId{
-				AssetId: subjectAssetId,
-			},
-		},
+		TransactionType:       oraclerpc.TransactionType_PURCHASE,
+		SubjectAsset:          rpcMarshalAssetSpecifier(assetSpecifier),
 		SubjectAssetMaxAmount: assetMaxAmount,
 		PaymentAsset: &oraclerpc.AssetSpecifier{
 			Id: &oraclerpc.AssetSpecifier_AssetId{