Fixed unit test after downloading covers from inventaire

internal/apitest/config_test/test.toml

@@ -5,5 +5,8 @@ database_file_path = "file::memory:?cache=shared"
 # The path to the sql file to load for demo data.
 demo_data_path = "../../demodata.sql"
 
+# Folder where uploaded files will be stored.
+image_folder_path = "/tmp"
+
 # The port to listen on for the server.
 port = "8080"