feat(etl-cache): add MarkdownCacheStore for cache blobs

surfsense_backend/app/etl_pipeline/cache/storage/markdown_store.py

@@ -0,0 +1,35 @@
+"""Read and write cached markdown blobs through the resolved backend."""
+
+from __future__ import annotations
+
+from app.etl_pipeline.cache.schemas import ParseKey
+from app.etl_pipeline.cache.storage.backend import resolve_cache_backend
+from app.etl_pipeline.cache.storage.object_keys import build_parse_object_key
+
+_MARKDOWN_CONTENT_TYPE = "text/markdown; charset=utf-8"
+
+
+class MarkdownCacheStore:
+    def __init__(self) -> None:
+        self._backend = resolve_cache_backend()
+
+    @property
+    def backend_name(self) -> str:
+        return self._backend.backend_name
+
+    async def save(self, key: ParseKey, markdown: str) -> str:
+        """Persist the markdown and return its storage key for the index row."""
+        storage_key = build_parse_object_key(key)
+        await self._backend.put(
+            storage_key,
+            markdown.encode("utf-8"),
+            content_type=_MARKDOWN_CONTENT_TYPE,
+        )
+        return storage_key
+
+    async def load(self, storage_key: str) -> str:
+        chunks = [chunk async for chunk in self._backend.open_stream(storage_key)]
+        return b"".join(chunks).decode("utf-8")
+
+    async def delete(self, storage_key: str) -> None:
+        await self._backend.delete(storage_key)