Authentication when embedding Power BI report in a public-facing web application

I have an externally facing web application that is not using Windows authentication (in fact ASP.NET Identity auth).  I have Power BI Report Server set up on prem as well.  I need to embed Power BI report in a page in the web application.  I know I can do it using URL access with parameter rs:embed=true.  Now, when I do that, it prompts browser login dialog because my users are outside my Windows domain.  But how do I deal with the authentication in this scenario?