Configure custom slack Oauth Install page using Bolt Django

configure.py

import slack_bolt.oauth.oauth_flow
from slack_bolt.oauth.oauth_flow import OAuthFlow
from slack_bolt.request import BoltRequest

class CustomPageOauthFlow(OAuthFlow):
    def build_install_page_html(self, url: str, request: BoltRequest) -> str:
        return 'Hello world!'

settings=OAuthSettings(
            client_id=client_id,
            client_secret=client_secret,
            scopes=scopes,
   
            installation_store=DjangoInstallationStore(
                client_id=client_id,
                logger=logger,
            ),
            
            state_store=DjangoOAuthStateStore(
                expiration_seconds=120,
                logger=logger,
            )
        )

app = App(
      oauth_flow=CustomPageOauthFlow(settings=settings),
      signing_secret=signing_secret,
      oauth_settings=settings
    )