core: add functions to serialize base tx info

That is, information without signatures (for v1) nor range
proofs and MGs (for v2)

src/cryptonote_basic/cryptonote_basic.h

@@ -250,6 +250,28 @@ namespace cryptonote
       }
     END_SERIALIZE()
 
+    template<bool W, template <bool> class Archive>
+    bool serialize_base(Archive<W> &ar)
+    {
+      FIELDS(*static_cast<transaction_prefix *>(this))
+
+      if (version == 1)
+      {
+      }
+      else
+      {
+        ar.tag("rct_signatures");
+        if (!vin.empty())
+        {
+          ar.begin_object();
+          bool r = rct_signatures.serialize_rctsig_base(ar, vin.size(), vout.size());
+          if (!r || !ar.stream().good()) return false;
+          ar.end_object();
+        }
+      }
+      return true;
+    }
+
   private:
     static size_t get_signature_size(const txin_v& tx_in);
   };

src/cryptonote_basic/cryptonote_format_utils.cpp

@@ -93,6 +93,16 @@ namespace cryptonote
     return true;
   }
   //---------------------------------------------------------------
+  bool parse_and_validate_tx_base_from_blob(const blobdata& tx_blob, transaction& tx)
+  {
+    std::stringstream ss;
+    ss << tx_blob;
+    binary_archive<false> ba(ss);
+    bool r = tx.serialize_base(ba);
+    CHECK_AND_ASSERT_MES(r, false, "Failed to parse transaction from blob");
+    return true;
+  }
+  //---------------------------------------------------------------
   bool parse_and_validate_tx_from_blob(const blobdata& tx_blob, transaction& tx, crypto::hash& tx_hash, crypto::hash& tx_prefix_hash)
   {
     std::stringstream ss;

src/cryptonote_basic/cryptonote_format_utils.h

@@ -44,6 +44,7 @@ namespace cryptonote
   crypto::hash get_transaction_prefix_hash(const transaction_prefix& tx);
   bool parse_and_validate_tx_from_blob(const blobdata& tx_blob, transaction& tx, crypto::hash& tx_hash, crypto::hash& tx_prefix_hash);
   bool parse_and_validate_tx_from_blob(const blobdata& tx_blob, transaction& tx);
+  bool parse_and_validate_tx_base_from_blob(const blobdata& tx_blob, transaction& tx);
   bool encrypt_payment_id(crypto::hash8 &payment_id, const crypto::public_key &public_key, const crypto::secret_key &secret_key);
   bool decrypt_payment_id(crypto::hash8 &payment_id, const crypto::public_key &public_key, const crypto::secret_key &secret_key);