refactor: move getFeePayer to STObject

include/xrpl/protocol/STObject.h

@@ -217,6 +217,11 @@ public:
     [[nodiscard]] AccountID
     getAccountID(SField const& field) const;
 
+    /** The account responsible for the fee and authorization: the delegate when
+        sfDelegate is present, otherwise the account. */
+    [[nodiscard]] AccountID
+    getFeePayer() const;
+
     [[nodiscard]] Blob
     getFieldVL(SField const& field) const;
     [[nodiscard]] STAmount const&

include/xrpl/protocol/STTx.h

@@ -84,9 +84,6 @@ public:
     [[nodiscard]] std::uint32_t
     getSeqValue() const;
 
-    [[nodiscard]] AccountID
-    getFeePayer() const;
-
     [[nodiscard]] boost::container::flat_set<AccountID>
     getMentionedAccounts() const;
 

include/xrpl/tx/transactors/system/Batch.h

@@ -25,9 +25,6 @@ public:
     static NotTEC
     preflightSigValidated(PreflightContext const& ctx);
 
-    static NotTEC
-    checkBatchSign(PreclaimContext const& ctx);
-
     static NotTEC
     checkSign(PreclaimContext const& ctx);
 
@@ -62,6 +59,12 @@ public:
         ttLOAN_MANAGE,
         ttLOAN_PAY,
     });
+
+private:
+    // Skips signature verification for inner txns, so keep it private: it must
+    // only be reached through Batch::checkSign.
+    static NotTEC
+    checkBatchSign(PreclaimContext const& ctx);
 };
 
 }  // namespace xrpl