feat(fetcher): add data fetcher

app/fetcher/beatmapset.py

@@ -0,0 +1,18 @@
+from __future__ import annotations
+
+from app.database.beatmapset import BeatmapsetResp
+
+from ._base import BaseFetcher
+
+from httpx import AsyncClient
+
+
+class BeatmapsetFetcher(BaseFetcher):
+    async def get_beatmap_set(self, beatmap_set_id: int) -> BeatmapsetResp:
+        async with AsyncClient() as client:
+            response = await client.get(
+                f"https://osu.ppy.sh/api/v2/beatmapsets/{beatmap_set_id}",
+                headers=self.header,
+            )
+            response.raise_for_status()
+            return BeatmapsetResp.model_validate(response.json())