Core: embed custom datapackage into .archipelago (#1288)

Co-authored-by: black-sliver <59490463+black-sliver@users.noreply.github.com>

MultiServer.py

@@ -124,6 +124,7 @@ class Context:
     stored_data_notification_clients: typing.Dict[str, typing.Set[Client]]
 
     item_names: typing.Dict[int, str] = Utils.KeyedDefaultDict(lambda code: f'Unknown item (ID:{code})')
+    item_name_groups: typing.Dict[str, typing.Dict[str, typing.Set[str]]]
     location_names: typing.Dict[int, str] = Utils.KeyedDefaultDict(lambda code: f'Unknown location (ID:{code})')
     all_item_and_group_names: typing.Dict[str, typing.Set[str]]
     forced_auto_forfeits: typing.Dict[str, bool]
@@ -202,7 +203,6 @@ class Context:
         self.non_hintable_names = collections.defaultdict(frozenset)
 
         self._load_game_data()
-        self._init_game_data()
 
     # Datapackage retrieval
     def _load_game_data(self):
@@ -412,6 +412,16 @@ class Context:
             server_options = decoded_obj.get("server_options", {})
             self._set_options(server_options)
 
+        # custom datapackage
+        for game_name, data in decoded_obj.get("datapackage", {}).items():
+            logging.info(f"Loading custom datapackage for game {game_name}")
+            self.gamespackage[game_name] = data
+            self.item_name_groups[game_name] = data["item_name_groups"]
+            del data["item_name_groups"]  # remove from datapackage, but keep in self.item_name_groups
+        self._init_game_data()
+        for game_name, data in self.item_name_groups.items():
+            self.read_data[f"item_name_groups_{game_name}"] = lambda lgame=game_name: self.item_name_groups[lgame]
+
     # saving
 
     def save(self, now=False) -> bool: