Add PermissionDelegation feature (#5354)

This change implements the account permission delegation described in XLS-75d, see https://github.com/XRPLF/XRPL-Standards/pull/257.

* Introduces transaction-level and granular permissions that can be delegated to other accounts.
* Adds `DelegateSet` transaction to grant specified permissions to another account.
* Adds `ltDelegate` ledger object to maintain the permission list for delegating/delegated account pair.
* Adds an optional `Delegate` field in common fields, allowing a delegated account to send transactions on behalf of the delegating account within the granted permission scope. The `Account` field remains the delegating account; the `Delegate` field specifies the delegated account. The transaction is signed by the delegated account.

src/test/jtx/impl/Env.cpp

@@ -465,7 +465,9 @@ Env::autofill_sig(JTx& jt)
         return jt.signer(*this, jt);
     if (!jt.fill_sig)
         return;
-    auto const account = lookup(jv[jss::Account].asString());
+    auto const account = jv.isMember(sfDelegate.jsonName)
+        ? lookup(jv[sfDelegate.jsonName].asString())
+        : lookup(jv[jss::Account].asString());
     if (!app().checkSigs())
     {
         jv[jss::SigningPubKey] = strHex(account.pk().slice());

src/test/jtx/impl/delegate.cpp

@@ -0,0 +1,67 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of rippled: https://github.com/ripple/rippled
+    Copyright (c) 2025 Ripple Labs Inc.
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose  with  or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#include <test/jtx/delegate.h>
+
+#include <xrpl/protocol/jss.h>
+
+namespace ripple {
+namespace test {
+namespace jtx {
+
+namespace delegate {
+
+Json::Value
+set(jtx::Account const& account,
+    jtx::Account const& authorize,
+    std::vector<std::string> const& permissions)
+{
+    Json::Value jv;
+    jv[jss::TransactionType] = jss::DelegateSet;
+    jv[jss::Account] = account.human();
+    jv[sfAuthorize.jsonName] = authorize.human();
+    Json::Value permissionsJson(Json::arrayValue);
+    for (auto const& permission : permissions)
+    {
+        Json::Value permissionValue;
+        permissionValue[sfPermissionValue.jsonName] = permission;
+        Json::Value permissionObj;
+        permissionObj[sfPermission.jsonName] = permissionValue;
+        permissionsJson.append(permissionObj);
+    }
+
+    jv[sfPermissions.jsonName] = permissionsJson;
+
+    return jv;
+}
+
+Json::Value
+entry(jtx::Env& env, jtx::Account const& account, jtx::Account const& authorize)
+{
+    Json::Value jvParams;
+    jvParams[jss::ledger_index] = jss::validated;
+    jvParams[jss::delegate][jss::account] = account.human();
+    jvParams[jss::delegate][jss::authorize] = authorize.human();
+    return env.rpc("json", "ledger_entry", to_string(jvParams));
+}
+
+}  // namespace delegate
+}  // namespace jtx
+}  // namespace test
+}  // namespace ripple

src/test/jtx/impl/mpt.cpp

@@ -233,6 +233,8 @@ MPTTester::set(MPTSet const& arg)
     }
     if (arg.holder)
         jv[sfHolder] = arg.holder->human();
+    if (arg.delegate)
+        jv[sfDelegate] = arg.delegate->human();
     if (submit(arg, jv) == tesSUCCESS && arg.flags.value_or(0))
     {
         auto require = [&](std::optional<Account> const& holder,