How to integrate the o365/m365 oauth flow with my slack app

Question

I'm writing an app which will allow me to get specific data from outlook/exchange using the EWS on behalf of a slack/outlook/exchange user. to authenticate via Microsoft’s oauth flow I created a azure a client_id and would like to initiate the oauth flow for m265 from the apps Home Screen. In order to create the client I’d I also need to provide a redirect url within azure ad.

Where can I find documentation on how to best use external oauth flows? (This is not about installing/authorizing the app within slack).

I’d like to add a "connect to outlook" button on my apps home page after installing from which to start the flow.

Shall I call the Microsoft login (oauth) url directly or should I first link to my apps web server? When calling the microsoft login I need to provide a redirect url (which needs to match the one in azure ad) to which the authorization codes gets returned.

For some apps (e.g. outlook calendar for slack) this seems be a slack url.

servicenow seems to use something like…

• https://slack.com/interop-apps/servicenow/snow_oauth_redirect

Is there a way to define such an url for my app within slack? How will the authorization code be handed over to my app (I assume to the Request url I defined for my app…?

Thank you for time and consideration..