Change squadrons to operate out of a single base.

https://github.com/dcs-liberation/dcs_liberation/issues/1145

Currently this is fixed at the start of the campaign. The squadron
locations are defined by the campaign file.

Follow up work:

* Track aircraft ownership per-squadron rather than per-airbase.
* UI for relocating squadrons.
* Ferry missions for squadrons that are relocating.
* Auto-relocation (probably only for retreat handling).

Fixes https://github.com/dcs-liberation/dcs_liberation/issues/1138

game/squadrons/pilot.py

@@ -0,0 +1,51 @@
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from enum import unique, Enum
+
+from faker import Faker
+
+
+@dataclass
+class PilotRecord:
+    missions_flown: int = field(default=0)
+
+
+@unique
+class PilotStatus(Enum):
+    Active = "Active"
+    OnLeave = "On leave"
+    Dead = "Dead"
+
+
+@dataclass
+class Pilot:
+    name: str
+    player: bool = field(default=False)
+    status: PilotStatus = field(default=PilotStatus.Active)
+    record: PilotRecord = field(default_factory=PilotRecord)
+
+    @property
+    def alive(self) -> bool:
+        return self.status is not PilotStatus.Dead
+
+    @property
+    def on_leave(self) -> bool:
+        return self.status is PilotStatus.OnLeave
+
+    def send_on_leave(self) -> None:
+        if self.status is not PilotStatus.Active:
+            raise RuntimeError("Only active pilots may be sent on leave")
+        self.status = PilotStatus.OnLeave
+
+    def return_from_leave(self) -> None:
+        if self.status is not PilotStatus.OnLeave:
+            raise RuntimeError("Only pilots on leave may be returned from leave")
+        self.status = PilotStatus.Active
+
+    def kill(self) -> None:
+        self.status = PilotStatus.Dead
+
+    @classmethod
+    def random(cls, faker: Faker) -> Pilot:
+        return Pilot(faker.name())