Feat (Core) Add CustomData to Groups (#17628)

* Add CustomData to Groups

* A one-line change and it STILL failed the first check run!

src/server/game/Groups/Group.h

@@ -18,6 +18,7 @@
 #ifndef AZEROTHCORE_GROUP_H
 #define AZEROTHCORE_GROUP_H
 
+#include "DataMap.h"
 #include "DBCEnums.h"
 #include "GroupRefMgr.h"
 #include "LootMgr.h"
@@ -318,6 +319,8 @@ public:
     void SetDifficultyChangePrevention(DifficultyPreventionChangeType type);
     void DoForAllMembers(std::function<void(Player*)> const& worker);
 
+    DataMap CustomData;
+
 protected:
     void _homebindIfInstance(Player* player);
     void _cancelHomebindIfInstance(Player* player);