Redirecting deep links after login

app/main.py

@@ -1,5 +1,6 @@
 from contextlib import asynccontextmanager
 from pathlib import Path
+from urllib.parse import quote
 
 from fastapi import FastAPI, Request
 from fastapi.middleware.cors import CORSMiddleware
@@ -45,7 +46,15 @@ def create_app() -> FastAPI:
 
     @app.exception_handler(NotAuthenticated)
     async def _redirect_to_login(request: Request, exc: NotAuthenticated):
-        return RedirectResponse(url="/login", status_code=302)
+        # Preserve the originally requested URL so we can return there after
+        # login. Only meaningful for GET navigations (the ones users deep-link).
+        login_url = "/login"
+        if request.method == "GET" and request.url.path not in ("/", "/login"):
+            target = request.url.path
+            if request.url.query:
+                target += "?" + request.url.query
+            login_url = f"/login?next={quote(target, safe='')}"
+        return RedirectResponse(url=login_url, status_code=302)
 
     @app.get("/healthz", tags=["health"])
     async def healthz():