Compatible with onAfterSetupMiddleware

[godky]

Note that app.get(...) in onAfterSetupMiddleware is not the same as app.get(...) in setupMiddlewares.

It seems app.get() in setupMiddlewares are always applied before middlewares are applied, if we have a config like this:

{
    onAfterSetupMiddleware: server => {
        server.app.get('/__index__.html', (req, res) => res.send('foo'));
    },
    config.historyApiFallback = {
        index: '/__index__.html',
        disableDotRule: true,
    };
}

The route /__index__.html will take place for history api fallback, however if we changed it to this:

{
    setupMiddlewares: (middlewares, server) => {
        server.app.get('/__index__.html', (req, res) => res.send('foo'));
        return middlewares;
    },
    config.historyApiFallback = {
        index: '/__index__.html',
        disableDotRule: true,
    };
}

History api fallback are broken, we have to transform it into a middleware like:

middlewares.unshift({
    path: '/__index__.html',
    handler: (req, res, next) => {
        if (req.method === 'GET') {
            res.send('foo');
        }
        else {
            next();
        }
    }
});

In this way we have to add a request.method check in middleware implementation.

Originally posted by @otakustay in #4129 (comment)

[godky]

Although there is a deprecate prompt, but the behavior of projects that used onAfterSetupMiddleware before will be inconsistent with the new version of webpack-dev-server