Create a checked, releasable type for laser codes.

The release behavior isn't used yet, but I'm working on pre-allocating
laser codes for front lines and flights to make it easier for players to
pick the laser codes for their weapons.

tests/lasercodes/test_lasercode.py

@@ -0,0 +1,75 @@
+import pytest
+
+from game.lasercodes import ILaserCodeRegistry
+from game.lasercodes.lasercode import LaserCode
+
+
+class MockRegistry(ILaserCodeRegistry):
+    def __init__(self) -> None:
+        self.release_count = 0
+
+    def alloc_laser_code(self) -> LaserCode:
+        raise NotImplementedError
+
+    def release_code(self, code: LaserCode) -> None:
+        self.release_count += 1
+
+
+@pytest.fixture(name="registry")
+def mock_registry() -> MockRegistry:
+    return MockRegistry()
+
+
+def test_lasercode_code(registry: ILaserCodeRegistry) -> None:
+
+    assert LaserCode(1688, registry).code == 1688
+
+    # 1113 doesn't comply to the rules, but is the only code valid for FC3 aircraft like
+    # the A-10A.
+    assert LaserCode(1113, registry).code == 1113
+
+    # The first digit must be 1
+    with pytest.raises(ValueError):
+        # And be exactly 4 digits
+        LaserCode(2688, registry)
+
+    # The code must be exactly 4 digits
+    with pytest.raises(ValueError):
+        LaserCode(888, registry)
+    with pytest.raises(ValueError):
+        LaserCode(18888, registry)
+
+    # 0 and 9 are invalid digits
+    with pytest.raises(ValueError):
+        LaserCode(1088, registry)
+    with pytest.raises(ValueError):
+        LaserCode(1608, registry)
+    with pytest.raises(ValueError):
+        LaserCode(1680, registry)
+    with pytest.raises(ValueError):
+        LaserCode(1988, registry)
+    with pytest.raises(ValueError):
+        LaserCode(1698, registry)
+    with pytest.raises(ValueError):
+        LaserCode(1689, registry)
+
+    # The second digit is further constrained to be 5, 6, or 7.
+    with pytest.raises(ValueError):
+        LaserCode(1188, registry)
+    with pytest.raises(ValueError):
+        LaserCode(1288, registry)
+    with pytest.raises(ValueError):
+        LaserCode(1388, registry)
+    with pytest.raises(ValueError):
+        LaserCode(1488, registry)
+    with pytest.raises(ValueError):
+        LaserCode(1888, registry)
+
+
+def test_lasercode_release(registry: MockRegistry) -> None:
+    code = LaserCode(1688, registry)
+    assert registry.release_count == 0
+    code.release()
+    assert registry.release_count == 1
+    code.release()
+    assert registry.release_count == 2