Asp.Net Core 2.2 Cookie Authentication in micro-service architecture

Question

I have 2 services, one web frontend and another backend. Authentication is done at the backed which includes JWT, Cookie, Session, etc. How does the CookieAuthenticationEvents work in this case, particularly with regards to OnRedirect<foo>? Are they web frontend-related events? How would the backed convey the OnRedirect<foo> back to the frontend service and then back to the client browser to redirect to the designated URL?