Remove SubscriptionId get and set functions

There are places to get or set subscription id differently like
`userSub.id` directly, or via `get/setSubscriptionId()` functions.

However, those aux functions are used only once and can be replaced to
access `userSub.id` directly.

Tested:
- Complies good
- Subscription GET and PATCH work correctly

Change-Id: I5cf81ba3ec0cb754387b40614e6309dca9a5305e
Signed-off-by: Myung Bae <myungbae@us.ibm.com>
diff --git a/redfish-core/include/event_service_manager.hpp b/redfish-core/include/event_service_manager.hpp
index 66e92d5..5a64472 100644
--- a/redfish-core/include/event_service_manager.hpp
+++ b/redfish-core/include/event_service_manager.hpp
@@ -474,17 +474,6 @@
         return eventSeqNum;
     }
 
-    void setSubscriptionId(const std::string& idIn)
-    {
-        BMCWEB_LOG_DEBUG("Subscription ID: {}", idIn);
-        userSub.id = idIn;
-    }
-
-    std::string getSubscriptionId() const
-    {
-        return userSub.id;
-    }
-
     bool matchSseId(const crow::sse_socket::Connection& thisConn)
     {
         return &thisConn == sseConn;
@@ -847,7 +836,7 @@
         }
 
         // Set Subscription ID for back trace
-        subValue->setSubscriptionId(id);
+        subValue->userSub.id = id;
 
         persistent_data::UserSubscription newSub(subValue->userSub);
 
@@ -958,8 +947,7 @@
             if (entryIsThisConn)
             {
                 persistent_data::EventServiceStore::getInstance()
-                    .subscriptionsConfigMap.erase(
-                        it->second->getSubscriptionId());
+                    .subscriptionsConfigMap.erase(entry->userSub.id);
                 it = subscriptionsMap.erase(it);
                 return;
             }