Qlik Sense does not make any Authentication, instead it relies on an external Identity Provider (IdP). Windoes Authentication is the default IdP for QlikSense. If you don't want Windows as IdP, you need to replace it with something else. Let me suppose your application already makes authentication, in this case you can use it as IdP. Qlik Sense can relies on your authentication module using the custom authentication (JWT, Ticket, header, session, and son on)..
If you want to know more, have a read here (https://help.qlik.com/en-US/sense/June2018/Subsystems/PlanningQlikSenseDeployments/Content/Deployment/Server-Security-Au…) for general informations and here (https://help.qlik.com/en-US/sense/June2018/Subsystems/PlanningQlikSenseDeployments/Content/Deployment/Server-Security-Au…) for the custom solution. And here (https://github.com/mhamano/qlik-session-auth) an example of Session authentication which probably suite the best your case
Thanks for the reply, but the help is more around 'how can I configure authentication in my Qlik Sense installation' while my question is more 'how can I authenticate from a web app to Qlik Sense'. Since this web app should potentially be used with different Sense installations, we want it to be as general as possible. We have a working solution that simply makes a HTTP GET, but we have just grabbed a file which we believe is in all Qlik Sense installtions - is this the way to go? This means that Qlik Sense does all tickets, cookies etc, which is great, but perhaps we need to handle that in our code?
As far as I understand the example it is a Node js solution, while we are working in the browser, which means we want the user to enter username/password or do whatever authentication procedure is necessary.