Warn when the ingest folder has no library to match

Without CWA_URL and CALIBRE_DB_PATH, each update goes to CWA as a new book.

tests/test_config.py

@@ -140,3 +140,18 @@ def test_prepare_without_cwa_creates_only_bindery_folders(monkeypatch, tmp_path,
     assert config.PERSONAL_INI.exists()
     assert {p.name for p in tmp_path.iterdir()} == {"config", "uploads", "tmp"}
     assert caplog.records == []
+
+
+@pytest.mark.parametrize(
+    ("url", "database", "warns"),
+    [("", None, True), ("https://cwa.invalid", None, False), ("", Path("/library/metadata.db"), False)],
+)
+def test_prepare_warns_about_an_ingest_folder_without_a_library(monkeypatch, tmp_path, caplog, url, database, warns):
+    monkeypatch.setattr(config, "CWA_URL", url)
+    monkeypatch.setattr(config, "CALIBRE_DB_PATH", database)
+    for name, folder in [("CONFIG_DIR", "config"), ("UPLOAD_DIR", "uploads"), ("TMP_DIR", "tmp"), ("INGEST_DIR", "in")]:
+        monkeypatch.setattr(config, name, tmp_path / folder)
+    monkeypatch.setattr(config, "PERSONAL_INI", tmp_path / "config" / "personal.ini")
+    with caplog.at_level("WARNING"):
+        config.prepare()
+    assert ("each update adds a new book" in caplog.text) is warns