Issue 3204 (#3458)

This issue addresses Issue #3204 by allowing factions to set a different
weapon introduction date.

game/factions/faction.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 import itertools
 import logging
 from dataclasses import dataclass, field
+import datetime
 from functools import cached_property
 from typing import Any, Dict, Iterator, List, Optional, TYPE_CHECKING, Type
 
@@ -118,6 +119,10 @@ class Faction:
     #: both will use it.
     unrestricted_satnav: bool = False
 
+    #: Overrides default weapons introduction years for faction. Maps names of
+    #: weapons groups to their introduction years.
+    weapons_introduction_year_overrides: Dict[str, int] = field(default_factory=dict)
+
     def has_access_to_dcs_type(self, unit_type: Type[DcsUnitType]) -> bool:
         # Vehicle and Ship Units
         if any(unit_type == u.dcs_unit_type for u in self.accessible_units):
@@ -262,6 +267,10 @@ class Faction:
 
         faction.unrestricted_satnav = json.get("unrestricted_satnav", False)
 
+        faction.weapons_introduction_year_overrides = json.get(
+            "weapons_introduction_year_overrides", {}
+        )
+
         return faction
 
     @property