feat: update codebase to use httpx2 and enhance docstrings for clarity

app/services/chat_session.py

@@ -17,13 +17,17 @@ from app.schemas.chat import ChatMessage
 
 @attrs.define(slots=True)
 class ChatSession:
+    """Conversation history associated with one websocket connection."""
+
     id: UUID = attrs.field(factory=uuid4)
     messages: list[ChatMessage] = attrs.field(factory=list)
 
     def add(self, message: ChatMessage) -> None:
+        """Append a message to this conversation."""
         self.messages.append(message)
 
     def history(self) -> list[ChatMessage]:
+        """Return a copy of the conversation history."""
         return list(self.messages)
 
 
@@ -35,23 +39,28 @@ class ChatSessionManager:
     """
 
     def __init__(self) -> None:
+        """Create an empty, lock-protected session registry."""
         self._sessions: dict[UUID, ChatSession] = {}
         self._lock = asyncio.Lock()
 
     async def create(self) -> ChatSession:
+        """Create and register a new conversation."""
         session = ChatSession()
         async with self._lock:
             self._sessions[session.id] = session
         return session
 
     async def get(self, session_id: UUID) -> ChatSession | None:
+        """Return the matching session, if it is active."""
         async with self._lock:
             return self._sessions.get(session_id)
 
     async def remove(self, session_id: UUID) -> None:
+        """Remove a session from the active registry."""
         async with self._lock:
             self._sessions.pop(session_id, None)
 
     async def count(self) -> int:
+        """Return the number of active sessions."""
         async with self._lock:
             return len(self._sessions)