Redfish(AccountService): Send the correct error message for the read only property

MinPasswordLength and MaxPasswordLength is a readOnly property
in the account service schema, so send the correct message
if the user tries to PATCH these properties.

Change-Id: If231ca13ef97fc05928435ac14a8190a186beb06
Signed-off-by: Ratan Gupta <ratagupt@linux.vnet.ibm.com>
diff --git a/redfish-core/lib/account_service.hpp b/redfish-core/lib/account_service.hpp
index 045f40c..1b7b4b8 100644
--- a/redfish-core/lib/account_service.hpp
+++ b/redfish-core/lib/account_service.hpp
@@ -167,12 +167,28 @@
 
         std::optional<uint32_t> unlockTimeout;
         std::optional<uint16_t> lockoutThreshold;
+        std::optional<uint16_t> minPasswordLength;
+        std::optional<uint16_t> maxPasswordLength;
+
         if (!json_util::readJson(req, res, "AccountLockoutDuration",
                                  unlockTimeout, "AccountLockoutThreshold",
-                                 lockoutThreshold))
+                                 lockoutThreshold, "MaxPasswordLength",
+                                 maxPasswordLength, "MinPasswordLength",
+                                 minPasswordLength))
         {
             return;
         }
+
+        if (minPasswordLength)
+        {
+            messages::propertyNotWritable(asyncResp->res, "MinPasswordLength");
+        }
+
+        if (maxPasswordLength)
+        {
+            messages::propertyNotWritable(asyncResp->res, "MaxPasswordLength");
+        }
+
         if (unlockTimeout)
         {
             crow::connections::systemBus->async_method_call(