feat(api): Raise 'correct' status code upon lookup error

While 404 clearly corresponds well to 'not found',
it is debatable whether we should return it, since the API
might have been used correctly in itself.

ancv/web/server.py

@@ -1,6 +1,7 @@
 from abc import ABC, abstractmethod
 from dataclasses import dataclass
 from datetime import timedelta
+from http import HTTPStatus
 from pathlib import Path
 from typing import AsyncGenerator, Optional
 
@@ -138,7 +139,7 @@ async def username(self, request: web.Request) -> web.Response:
         except ResumeLookupError as e:
             stopwatch.stop()
             log.warning(str(e))
-            return web.Response(text=str(e))
+            return web.Response(text=str(e), status=HTTPStatus.NOT_FOUND)
         else:
             stopwatch(segment="Templating")
             try: