[IMPROVE] [Apps-Engine] App user as the default notifier

[shiqimei]

Depends on RocketChat/Rocket.Chat.Apps-engine#255

Closes #17046

[shiqimei]

The app for testing:

import {
    IAppAccessors,
    IHttp,
    ILogger,
    IModify,
    IPersistence,
    IRead,
} from '@rocket.chat/apps-engine/definition/accessors';
import { App } from '@rocket.chat/apps-engine/definition/App';
import { IMessage, IPostMessageSent } from '@rocket.chat/apps-engine/definition/messages';
import { IAppInfo } from '@rocket.chat/apps-engine/definition/metadata';

export class NotifyUserApp extends App implements IPostMessageSent {
    constructor(info: IAppInfo, logger: ILogger, accessors: IAppAccessors) {
        super(info, logger, accessors);
    }

    public async executePostMessageSent(message: IMessage, read: IRead, http: IHttp, persistence: IPersistence, modify: IModify): Promise<void> {
        const { sender, room, text } = message;
        const messageBuilder = modify.getCreator().startMessage({ room, text } as IMessage);

        await read.getNotifier().notifyUser(sender, messageBuilder.getMessage());
        await read.getNotifier().notifyUser(sender, message);

        await read.getNotifier().notifyRoom(room, messageBuilder.getMessage());
        return read.getNotifier().notifyRoom(room, message);
    }
}

Result: