feat: implement auth callback page

This page will allow users to redirect to their previous path when they sign in.

src/pages/mod.rs

@@ -9,8 +9,10 @@ mod test_page;
 mod unauthenticated_page;
 mod utils;
 mod provider_contact;
+mod auth_callback;
 
 pub use self::{
     about_page::*, comparison_test::*, home_page::*, loaner_page::*, provider_portal::*,
-    test_page::*, unauthenticated_page::*, scholarship_info::*, provider_contact::*
+    test_page::*, unauthenticated_page::*, scholarship_info::*, provider_contact::*,
+    auth_callback::*,
 };