Persist Sapling payment address to IVK map

This ensures we remember any diversified addresses manually generated
outside the wallet.

src/wallet/wallet.cpp

@@ -174,6 +174,28 @@ bool CWallet::AddSaplingZKey(
     return true;
 }
 
+// Add payment address -> incoming viewing key map entry
+bool CWallet::AddSaplingIncomingViewingKey(
+    const libzcash::SaplingIncomingViewingKey &ivk,
+    const libzcash::SaplingPaymentAddress &addr)
+{
+    AssertLockHeld(cs_wallet); // mapSaplingZKeyMetadata
+
+    if (!CCryptoKeyStore::AddSaplingIncomingViewingKey(ivk, addr)) {
+        return false;
+    }
+
+    if (!fFileBacked) {
+        return true;
+    }
+
+    if (!IsCrypted()) {
+        return CWalletDB(strWalletFile).WriteSaplingPaymentAddress(addr, ivk);
+    }
+
+    return true;
+}
+
 
 // Add spending key to keystore and persist to disk
 bool CWallet::AddSproutZKey(const libzcash::SproutSpendingKey &key)
@@ -365,6 +387,13 @@ bool CWallet::LoadSaplingZKey(const libzcash::SaplingExtendedSpendingKey &key)
     return CCryptoKeyStore::AddSaplingSpendingKey(key, key.DefaultAddress());
 }
 
+bool CWallet::LoadSaplingPaymentAddress(
+    const libzcash::SaplingPaymentAddress &addr,
+    const libzcash::SaplingIncomingViewingKey &ivk)
+{
+    return CCryptoKeyStore::AddSaplingIncomingViewingKey(ivk, addr);
+}
+
 bool CWallet::LoadZKey(const libzcash::SproutSpendingKey &key)
 {
     return CCryptoKeyStore::AddSproutSpendingKey(key);