Combine Issue/MPTIssue handling in Payment transactor plus other changes

* Add support for DeliverMin and partial payment
* Fix error for non-existent issuance payment
* Update unit-tests
* Refactor unit-test for tx with non-MPT amounts

include/xrpl/protocol/Asset.h

@@ -94,6 +94,9 @@ class Asset
 
     friend constexpr bool
     operator!=(Asset const& lhs, Asset const& rhs);
+
+    friend constexpr bool
+    operator==(Currency const& lhs, Asset const& rhs);
 };
 
 template <ValidIssueType TIss>
@@ -148,6 +151,12 @@ operator!=(Asset const& lhs, Asset const& rhs)
     return !(lhs == rhs);
 }
 
+constexpr bool
+operator==(Currency const& lhs, Asset const& rhs)
+{
+    return rhs.holds<Issue>() && rhs.get<Issue>().currency == lhs;
+}
+
 inline bool
 isXRP(Asset const& asset)
 {

include/xrpl/protocol/MPTIssue.h

@@ -76,6 +76,8 @@ operator!=(MPTIssue const& lhs, MPTIssue const& rhs)
     return !(lhs == rhs);
 }
 
+/** MPT is a non-native token.
+ */
 inline bool
 isXRP(MPTID const&)
 {

include/xrpl/protocol/Rate.h

@@ -74,7 +74,7 @@ STAmount
 multiplyRound(
     STAmount const& amount,
     Rate const& rate,
-    Issue const& issue,
+    Asset const& asset,
     bool roundUp);
 
 STAmount
@@ -87,7 +87,7 @@ STAmount
 divideRound(
     STAmount const& amount,
     Rate const& rate,
-    Issue const& issue,
+    Asset const& issue,
     bool roundUp);
 
 namespace nft {

src/libxrpl/protocol/MPTIssue.cpp

@@ -30,6 +30,8 @@ MPTIssue::MPTIssue(MPTID const& issuanceID) : mptID_(issuanceID)
 AccountID const&
 MPTIssue::getIssuer() const
 {
+    // MPTID is concatenation of sequence + account
+    static_assert(sizeof(MPTID) == (sizeof(std::uint32_t) + sizeof(AccountID)));
     // copy from id skipping the sequence
     AccountID const* account = reinterpret_cast<AccountID const*>(
         mptID_.data() + sizeof(std::uint32_t));

src/libxrpl/protocol/Rate2.cpp

@@ -69,7 +69,7 @@ STAmount
 multiplyRound(
     STAmount const& amount,
     Rate const& rate,
-    Issue const& issue,
+    Asset const& asset,
     bool roundUp)
 {
     assert(rate.value != 0);
@@ -79,7 +79,7 @@ multiplyRound(
         return amount;
     }
 
-    return mulRound(amount, detail::as_amount(rate), issue, roundUp);
+    return mulRound(amount, detail::as_amount(rate), asset, roundUp);
 }
 
 STAmount
@@ -90,7 +90,7 @@ divide(STAmount const& amount, Rate const& rate)
     if (rate == parityRate)
         return amount;
 
-    return divide(amount, detail::as_amount(rate), amount.issue());
+    return divide(amount, detail::as_amount(rate), amount.asset());
 }
 
 STAmount
@@ -101,22 +101,22 @@ divideRound(STAmount const& amount, Rate const& rate, bool roundUp)
     if (rate == parityRate)
         return amount;
 
-    return divRound(amount, detail::as_amount(rate), amount.issue(), roundUp);
+    return divRound(amount, detail::as_amount(rate), amount.asset(), roundUp);
 }
 
 STAmount
 divideRound(
     STAmount const& amount,
     Rate const& rate,
-    Issue const& issue,
+    Asset const& asset,
     bool roundUp)
 {
     assert(rate.value != 0);
 
     if (rate == parityRate)
         return amount;
 
-    return divRound(amount, detail::as_amount(rate), issue, roundUp);
+    return divRound(amount, detail::as_amount(rate), asset, roundUp);
 }
 
 }  // namespace ripple

src/libxrpl/protocol/TxFormats.cpp

@@ -167,7 +167,7 @@ TxFormats::TxFormats()
             {sfPaths, soeDEFAULT},
             {sfInvoiceID, soeOPTIONAL},
             {sfDestinationTag, soeOPTIONAL},
-            {sfDeliverMin, soeOPTIONAL},
+            {sfDeliverMin, soeOPTIONAL, soeMPTSupported},
         },
         commonFields);