Start adding transaction layouts, flags, and fields

(Does not compile)

src/libxrpl/protocol/InnerObjectFormats.cpp

@@ -28,6 +28,12 @@ InnerObjectFormats::InnerObjectFormats()
     // inner objects with the default fields have to be
     // constructed with STObject::makeInnerObject()
 
+    std::initializer_list<SOElement> const signingFields = {
+        {sfAccount, soeREQUIRED},
+        {sfSigningPubKey, soeREQUIRED},
+        {sfTxnSignature, soeREQUIRED},
+    };
+
     add(sfSignerEntry.jsonName,
         sfSignerEntry.getCode(),
         {
@@ -36,13 +42,7 @@ InnerObjectFormats::InnerObjectFormats()
             {sfWalletLocator, soeOPTIONAL},
         });
 
-    add(sfSigner.jsonName,
-        sfSigner.getCode(),
-        {
-            {sfAccount, soeREQUIRED},
-            {sfSigningPubKey, soeREQUIRED},
-            {sfTxnSignature, soeREQUIRED},
-        });
+    add(sfSigner.jsonName, sfSigner.getCode(), signingFields);
 
     add(sfMajority.jsonName,
         sfMajority.getCode(),
@@ -154,6 +154,10 @@ InnerObjectFormats::InnerObjectFormats()
             {sfIssuer, soeREQUIRED},
             {sfCredentialType, soeREQUIRED},
         });
+
+    add(sfCounterpartySignature.jsonName,
+        sfCounterpartySignature.getCode(),
+        signingFields);
 }
 
 InnerObjectFormats const&