Store CreatureIndex on Creature, includes helper function to get a creatures party from a battle.

Signed-off-by: Deukhoofd <Deukhoofd@gmail.com>

src/Battling/Models/Battle.cpp

@@ -209,3 +209,23 @@ Battle* Battle::Clone() const {
 
     return battle;
 }
+ArbUt::OptionalBorrowedPtr<BattleParty> Battle::FindPartyForCreature(const ArbUt::BorrowedPtr<Creature>& creature) {
+    if (creature->IsOnBattleField()) {
+        auto index = creature->GetBattleIndex();
+        for (auto& party : _parties) {
+            if (!party->IsResponsibleForIndex(index)) {
+                continue;
+            }
+            if (party->GetParty()->HasCreature(creature)) {
+                return party;
+            }
+        }
+    } else {
+        for (auto& party : _parties) {
+            if (party->GetParty()->HasCreature(creature)) {
+                return party;
+            }
+        }
+    }
+    return {};
+}