change that GameplayDatabase can have different backends, sqlite and postgresql with a Template example backend

tests/test_GameplayDatabase.py

@@ -3,7 +3,7 @@ import unittest
 from pathlib import Path
 import tempfile, sqlite3
 
-from server.database import GameplayDatabase
+from server.database import GameplayDatabase, GameplayBackendBuilder
 
 class TestGameplayDatabase(unittest.IsolatedAsyncioTestCase):
   def _build_state(self, turn:int, me_head:tuple[int, int], enemy_head:tuple[int, int], include_enemy:bool=True) -> dict:
@@ -57,7 +57,7 @@ class TestGameplayDatabase(unittest.IsolatedAsyncioTestCase):
   async def test_records_gameplay_with_wal_and_inferred_moves(self):
     with tempfile.TemporaryDirectory() as temp_dir:
       db_path = Path(temp_dir) / "gameplay.sqlite3"
-      database = GameplayDatabase(str(db_path), busy_timeout_ms=4000)
+      database = GameplayDatabase(GameplayBackendBuilder.build(db_path=str(db_path), busy_timeout_ms=4000))
 
       await database.record_game_start(self._build_state(turn=0, me_head=(1, 1), enemy_head=(5, 5)))
       await database.record_turn(