Blazor Webassembly - JWT in headers (before my app)

Question

How can I use a JWT which is issued upstream of my application (Webassembly hosted by ASP.NET Core)?

1. The customer clicks on the URL www.example.com
2. An external provider takes care of the authentication (before my Blazor app - Webassembly hosted by ASP.NET Core)
3. The external provider redirects the user to www.example.com/myblazorapp with the JWT in the headers
4. "MyBlazorApp" must retrieve this JWT and use it during future calls to APIs