initial commit after split

src/govoplan_campaign/backend/services/attachment_matching.py

@@ -0,0 +1,13 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+from govoplan_campaign.backend.domain.campaign import MailAttachmentConfig
+
+
+def match_files(base_path: Path, config: MailAttachmentConfig) -> list[Path]:
+    directory = base_path / config.base_dir
+    if not directory.exists():
+        return []
+    iterator = directory.rglob(config.file_filter) if config.include_subdirs else directory.glob(config.file_filter)
+    return sorted(path for path in iterator if path.is_file() and path.stat().st_size >= 0)