Function session

session<S = Record<string, unknown>>(options?: SessionOptions<S>): MiddlewareFn
Creates a session management middleware.

Automatically loads user or chat session state before handlers execute, exposes context.session, and persists modified state after execution finishes.
Type Parameters
- S = Record<string, unknown>
  Structure of the session state.
Parameters
- options: SessionOptions<S> = {}
  Configuration options for initial state and storage backend.
Returns MiddlewareFn
A MiddlewareFn ready to be used with app.use().
Example
```
interface MySession {
  count: number;
}

app.use(session<MySession>({
  initial: () => ({ count: 0 }),
}));

app.addHandler(new CommandHandler("counter", async (update, context) => {
  const ctx = context as CallbackContext & { session: MySession };
  ctx.session.count++;
  await context.bot.sendMessage({
    chat_id: update.effective_chat!.id,
    text: `You have called this command ${session.count} times!`,
  });
}));
```