rpc, doc: encryptwallet, mention HD seed rotation and new backup

Better to notify users about the HD seed rotation and the new
backup requirement before executing the encryption process.
Ensuring they are prepared to update previous backups and
securely safeguard the updated wallet file.

Co-authored-by: jonatack <jon@atack.com>

Author: furszy

src/wallet/rpc/encrypt.cpp

@@ -220,7 +220,11 @@ RPCHelpMan encryptwallet()
                 "After this, any calls that interact with private keys such as sending or signing \n"
                 "will require the passphrase to be set prior the making these calls.\n"
                 "Use the walletpassphrase call for this, and then walletlock call.\n"
-                "If the wallet is already encrypted, use the walletpassphrasechange call.\n",
+                "If the wallet is already encrypted, use the walletpassphrasechange call.\n"
+                "** IMPORTANT **\n"
+                "For security reasons, the encryption process will generate a new HD seed, resulting\n"
+                "in the creation of a fresh set of active descriptors. Therefore, it is crucial to\n"
+                "securely back up the newly generated wallet file using the backupwallet RPC.\n",
                 {
                     {"passphrase", RPCArg::Type::STR, RPCArg::Optional::NO, "The pass phrase to encrypt the wallet with. It must be at least 1 character, but should be long."},
                 },
@@ -268,7 +272,7 @@ RPCHelpMan encryptwallet()
         throw JSONRPCError(RPC_WALLET_ENCRYPTION_FAILED, "Error: Failed to encrypt the wallet.");
     }
 
-    return "wallet encrypted; The keypool has been flushed and a new HD seed was generated (if you are using HD). You need to make a new backup.";
+    return "wallet encrypted; The keypool has been flushed and a new HD seed was generated. You need to make a new backup with the backupwallet RPC.";
 },
     };
 }