Maintain composition when buying ground units.

Unit composition is defined by the doctrine. The most understaffed CP
will now get the most underrepresented unit type. Previously a random
understaffed CP would get a random unit type.

Fixes https://github.com/dcs-liberation/dcs_liberation/issues/1057.

game/factions/faction.py

@@ -1,4 +1,5 @@
 from __future__ import annotations
+from game.data.groundunitclass import GroundUnitClass
 
 import logging
 from dataclasses import dataclass, field
@@ -133,6 +134,16 @@ class Faction:
     #: both will use it.
     unrestricted_satnav: bool = False
 
+    def has_access_to_unittype(self, unitclass: GroundUnitClass) -> bool:
+        has_access = False
+        for vehicle in unitclass.unit_list:
+            if vehicle in self.frontline_units:
+                return True
+            if vehicle in self.artillery_units:
+                return True
+
+        return has_access
+
     @classmethod
     def from_json(cls: Type[Faction], json: Dict[str, Any]) -> Faction:
         faction = Faction(locales=json.get("locales"))