feat(auth): implement auth stack

app/db.py

@@ -2,8 +2,10 @@
 
 from collections.abc import AsyncGenerator
 from contextlib import asynccontextmanager
+from contextvars import ContextVar
 
 import asyncpg
+from asyncpg.pool import PoolConnectionProxy
 import redis.asyncio as redis
 
 
@@ -27,7 +29,7 @@ class Database:
             await self.pool.close()
 
     @asynccontextmanager
-    async def connection(self) -> AsyncGenerator[asyncpg.Connection, None]:
+    async def connection(self) -> AsyncGenerator[asyncpg.Connection | PoolConnectionProxy, None]:
         """Acquire a connection from the pool."""
         if not self.pool:
             raise RuntimeError("Database not connected")
@@ -35,7 +37,7 @@ class Database:
             yield conn
 
     @asynccontextmanager
-    async def transaction(self) -> AsyncGenerator[asyncpg.Connection, None]:
+    async def transaction(self) -> AsyncGenerator[asyncpg.Connection | PoolConnectionProxy, None]:
         """Acquire a connection with an active transaction."""
         if not self.pool:
             raise RuntimeError("Database not connected")
@@ -74,7 +76,26 @@ db = Database()
 redis_client = RedisClient()
 
 
-async def get_conn() -> AsyncGenerator[asyncpg.Connection, None]:
-    """Dependency for getting a database connection."""
-    async with db.connection() as conn:
-        yield conn
+_connection_ctx: ContextVar[asyncpg.Connection | PoolConnectionProxy | None] = ContextVar(
+    "db_connection",
+    default=None,
+)
+
+
+async def get_conn() -> AsyncGenerator[asyncpg.Connection | PoolConnectionProxy, None]:
+    """Dependency that reuses the same DB connection within a request context."""
+
+    existing_conn = _connection_ctx.get()
+    if existing_conn is not None:
+        yield existing_conn
+        return
+
+    if not db.pool:
+        raise RuntimeError("Database not connected")
+
+    async with db.pool.acquire() as conn:
+        token = _connection_ctx.set(conn)
+        try:
+            yield conn
+        finally:
+            _connection_ctx.reset(token)