Payment tx fee payer ID (#7682)

include/xrpl/protocol/STTx.h

@@ -141,6 +141,9 @@ public:
     [[nodiscard]] std::vector<uint256> const&
     getBatchTransactionIDs() const;
 
+    [[nodiscard]] AccountID
+    getFeePayerID() const;
+
 private:
     /** Check the signature.
         @param rules The current ledger rules.

include/xrpl/tx/Transactor.h

@@ -137,7 +137,8 @@ enum class FeePayerType {
 
 struct FeePayer
 {
-    Keylet entry;
+    AccountID id;
+    Keylet keylet;
     SF_AMOUNT const& balanceField;
     FeePayerType type{FeePayerType::Account};
 };
@@ -317,6 +318,7 @@ public:
 
     static NotTEC
     checkSponsor(ReadView const& view, STTx const& tx);
+
     /////////////////////////////////////////////////////
 
     // Interface used by AccountDelete