rpc: Add parent descriptor to getaddressinfo output

Adds parent_desc field to getaddressinfo output which contains the
descriptor that was used to derive the address if it is available.

src/wallet/rpcwallet.cpp

@@ -3663,6 +3663,7 @@ UniValue getaddressinfo(const JSONRPCRequest& request)
                         {RPCResult::Type::BOOL, "iswatchonly", "If the address is watchonly."},
                         {RPCResult::Type::BOOL, "solvable", "If we know how to spend coins sent to this address, ignoring the possible lack of private keys."},
                         {RPCResult::Type::STR, "desc", /* optional */ true, "A descriptor for spending coins sent to this address (only when solvable)."},
+                        {RPCResult::Type::STR, "parent_desc", /* optional */ true, "The descriptor used to derive this address if this is a descriptor wallet"},
                         {RPCResult::Type::BOOL, "isscript", "If the key is a script."},
                         {RPCResult::Type::BOOL, "ischange", "If the address was used for change output."},
                         {RPCResult::Type::BOOL, "iswitness", "If the address is a witness address."},
@@ -3732,6 +3733,14 @@ UniValue getaddressinfo(const JSONRPCRequest& request)
        ret.pushKV("desc", InferDescriptor(scriptPubKey, *provider)->ToString());
     }
 
+    DescriptorScriptPubKeyMan* desc_spk_man = dynamic_cast<DescriptorScriptPubKeyMan*>(pwallet->GetScriptPubKeyMan(scriptPubKey));
+    if (desc_spk_man) {
+        std::string desc_str;
+        if (desc_spk_man->GetDescriptorString(desc_str, false)) {
+            ret.pushKV("parent_desc", desc_str);
+        }
+    }
+
     ret.pushKV("iswatchonly", bool(mine & ISMINE_WATCH_ONLY));
 
     UniValue detail = DescribeWalletAddress(pwallet, dest);