First shot at supporting custom handler

app/utils/custom_index_handler.py

@@ -0,0 +1,32 @@
+from typing import Any
+from typing import Awaitable
+from typing import Callable
+
+from fastapi import Depends
+from fastapi import Request
+from fastapi.responses import JSONResponse
+
+from app.actor import LOCAL_ACTOR
+from app.config import is_activitypub_requested
+from app.database import AsyncSession
+from app.database import get_db_session
+
+_Handler = Callable[[Request, AsyncSession], Awaitable[Any]]
+
+
+def build_custom_index_handler(handler: _Handler) -> _Handler:
+    async def custom_index(
+        request: Request,
+        db_session: AsyncSession = Depends(get_db_session),
+    ) -> Any:
+        # Serve the AP actor if requested
+        if is_activitypub_requested(request):
+            return JSONResponse(
+                LOCAL_ACTOR.ap_actor,
+                media_type="application/activity+json",
+            )
+
+        # Defer to the custom handler
+        return await handler(request, db_session)
+
+    return custom_index