Add Permission Delegation sample code

_code-samples/delegate-permissions/js/use-delegated-permissions.js

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+const xrpl = require('xrpl')
+const readline = require('readline').createInterface({
+  input: process.stdin,
+  output: process.stdout
+})
+const { stringToHex, hexToString } = require('@xrplf/isomorphic/utils')
+
+// Set delegating account and delegate from user input
+readline.question(`Address of delegating account? `, async function(from_address) {
+  readline.question(`Delegate's secret key? `, async function(secret) {
+    const client = new xrpl.Client("wss://s.devnet.rippletest.net:51233")
+    await client.connect()
+
+    const delegate_wallet = xrpl.Wallet.fromSeed(secret)
+    console.log(`Using delegate address ${delegate_wallet.address}`)
+
+    // Check which permissions the delegate has been granted, if any
+    response = await client.request({
+        "command": "account_objects",
+        "account": from_address,
+        "type": "delegate",
+        "ledger_index": "validated"
+    })
+    let found_match = false
+    for (delegate_entry of response.result.account_objects) {
+      if (delegate_entry.Account == from_address && delegate_entry.Authorize == delegate_wallet.address) {
+        found_match = true
+        console.log("Delegate has the following permissions:")
+        for (perm of delegate_entry.Permissions) {
+          console.log(perm.Permission.PermissionValue)
+        }
+        break
+      }
+    }
+    if (!found_match) {
+      console.warn("Delegate appears not to have any permissions granted by delegating account.")
+      console.warn("Did you run delegate-permissions.js first with your delegate address?")
+      return
+    }
+
+    // Use the AccountDomainSet granular permission to set the "Domain" field
+    // of the delegating account
+    const set_domain_example = {
+      "TransactionType": "AccountSet",
+      "Account": from_address,
+      "Delegate": delegate_wallet.address,
+      "Domain": stringToHex("example.com")
+    }
+
+    // Prepare, sign, and submit the transaction
+    const prepared = await client.autofill(set_domain_example)
+    const signed = delegate_wallet.sign(prepared)
+    console.log("Submitting transaction:")
+    console.log(JSON.stringify(signed, null, 2))
+    const result = await client.submitAndWait(signed.tx_blob)
+
+    // Check transaction results and disconnect
+    console.log(result)
+    if (result.result.meta.TransactionResult === "tesSUCCESS") {
+      console.log("Transaction successful.")
+    }
+
+    // Confirm that the account's Domain field has been set as expected
+    const account_info_resp = await client.request({
+      "command": "account_info",
+      "account": from_address,
+      "ledger_index": "validated"
+    })
+    const domain_str = hexToString(account_info_resp.result.account_data.Domain)
+    console.log(`Domain is ${domain_str}`)
+
+    client.disconnect()
+  })
+})