Add Orchard to change address generation

src/wallet/wallet.cpp

@@ -1901,6 +1901,9 @@ std::optional<RecipientAddress> CWallet::GenerateChangeAddressForAccount(
             for (OutputPool t : changeOptions) {
                 std::optional<RecipientAddress> changeAddr;
                 switch (t) {
+                case OutputPool::Orchard:
+                    changeAddr = ufvk.value().GetChangeAddress(OrchardChangeRequest());
+                    break;
                 case OutputPool::Sapling:
                     changeAddr = ufvk.value().GetChangeAddress(SaplingChangeRequest());
                     break;

src/zcash/address/orchard.cpp

@@ -43,6 +43,10 @@ uint256 OrchardFullViewingKey::ToInternalOutgoingViewingKey() const {
     return ovk;
 }
 
+OrchardRawAddress OrchardFullViewingKey::GetChangeAddress() const {
+    return ToInternalIncomingViewingKey().Address(0);
+}
+
 OrchardSpendingKey OrchardSpendingKey::ForAccount(
         const HDSeed& seed,
         uint32_t bip44CoinType,

src/zcash/address/orchard.hpp

@@ -206,6 +206,8 @@ public:
 
     uint256 ToInternalOutgoingViewingKey() const;
 
+    libzcash::OrchardRawAddress GetChangeAddress() const;
+
     OrchardFullViewingKey& operator=(OrchardFullViewingKey&& key)
     {
         if (this != &key) {

src/zcash/address/unified.cpp

@@ -175,16 +175,23 @@ std::optional<RecipientAddress> ZcashdUnifiedFullViewingKey::GetChangeAddress(co
             }
         },
         [&](const SaplingChangeRequest& req) {
-            // currently true by construction, as a UFVK must have a supported shielded component
             if (saplingKey.has_value()) {
                 addr = saplingKey.value().GetChangeAddress();
             }
+        },
+        [&](const OrchardChangeRequest& req) {
+            if (orchardKey.has_value()) {
+                addr = orchardKey.value().GetChangeAddress();
+            }
         }
     }, req);
     return addr;
 }
 
 std::optional<RecipientAddress> ZcashdUnifiedFullViewingKey::GetChangeAddress() const {
+    if (orchardKey.has_value()) {
+        return orchardKey.value().GetChangeAddress();
+    }
     if (saplingKey.has_value()) {
         return saplingKey.value().GetChangeAddress();
     }

src/zcash/address/unified.h

@@ -58,10 +58,12 @@ public:
 };
 
 class SaplingChangeRequest {};
+class OrchardChangeRequest {};
 
 typedef std::variant<
     TransparentChangeRequest,
-    SaplingChangeRequest> ChangeRequest;
+    SaplingChangeRequest,
+    OrchardChangeRequest> ChangeRequest;
 
 /**
  * Test whether the specified list of receiver types contains a