Core/Player: Always allow accounts with RBAC_PERM_COMMAND_GM to enter instances on login

Always allow accounts with RBAC_PERM_COMMAND_GM to enter instances on login even if player had .gm off .
Send an ingame message to notify the user about the avoided kick.

src/server/game/Entities/Player/Player.cpp

@@ -2561,6 +2561,11 @@ void Player::SetGameMaster(bool on)
     UpdateObjectVisibility();
 }
 
+bool Player::CanBeGameMaster() const
+{
+    return m_session && m_session->HasPermission(rbac::RBAC_PERM_COMMAND_GM);
+}
+
 void Player::SetGMVisible(bool on)
 {
     if (on)
@@ -18674,17 +18679,28 @@ bool Player::CheckInstanceLoginValid(Map* map)
     {
         // cannot be in raid instance without a group
         if (!GetGroup())
-            return false;
+            return IsInstanceLoginGameMasterException();
     }
     else
     {
         // cannot be in normal instance without a group and more players than 1 in instance
         if (!GetGroup() && map->GetPlayersCountExceptGMs() > 1)
-            return false;
+            return IsInstanceLoginGameMasterException();
     }
 
     // do checks for satisfy accessreqs, instance full, encounter in progress (raid), perm bind group != perm bind player
-    return sMapMgr->CanPlayerEnter(map->GetId(), this, true);
+    return sMapMgr->CanPlayerEnter(map->GetId(), this, true) || IsInstanceLoginGameMasterException();
+}
+
+bool Player::IsInstanceLoginGameMasterException() const
+{
+    if (CanBeGameMaster())
+    {
+        ChatHandler(GetSession()).PSendSysMessage("You didn't get kicked out of the instance even if Player::CheckInstanceLoginValid() returned false and without .gm on flag");
+        return true;
+    }
+    else
+        return false;
 }
 
 bool Player::CheckInstanceCount(uint32 instanceId) const

src/server/game/Entities/Player/Player.h

@@ -1072,6 +1072,7 @@ class Player : public Unit, public GridObject<Player>
         bool isAcceptWhispers() const { return (m_ExtraFlags & PLAYER_EXTRA_ACCEPT_WHISPERS) != 0; }
         void SetAcceptWhispers(bool on) { if (on) m_ExtraFlags |= PLAYER_EXTRA_ACCEPT_WHISPERS; else m_ExtraFlags &= ~PLAYER_EXTRA_ACCEPT_WHISPERS; }
         bool IsGameMaster() const { return (m_ExtraFlags & PLAYER_EXTRA_GM_ON) != 0; }
+        bool CanBeGameMaster() const;
         void SetGameMaster(bool on);
         bool isGMChat() const { return (m_ExtraFlags & PLAYER_EXTRA_GM_CHAT) != 0; }
         void SetGMChat(bool on) { if (on) m_ExtraFlags |= PLAYER_EXTRA_GM_CHAT; else m_ExtraFlags &= ~PLAYER_EXTRA_GM_CHAT; }
@@ -2500,6 +2501,8 @@ class Player : public Unit, public GridObject<Player>
         bool IsHasDelayedTeleport() const { return m_bHasDelayedTeleport; }
         void SetDelayedTeleportFlag(bool setting) { m_bHasDelayedTeleport = setting; }
         void ScheduleDelayedOperation(uint32 operation) { if (operation < DELAYED_END) m_DelayedOperations |= operation; }
+        
+        bool IsInstanceLoginGameMasterException() const;
 
         MapReference m_mapRef;