A Kotoba.Storage adapter that keeps files in a directory on the local disk.

# config/config.exs
config :kotoba, storage: Kotoba.Storage.Local

# config/runtime.exs, in the :prod block
if config_env() == :prod do
  config :kotoba, Kotoba.Storage.Local,
    root: System.get_env("KOTOBA_UPLOADS", "/var/lib/my_app/uploads"),
    url_prefix: "/uploads/kotoba"
end

# config/dev.exs
config :kotoba, Kotoba.Storage.Local, root: Path.expand("../tmp/uploads", __DIR__)

• :root - the directory for the files (required). In production, give an absolute path outside the release, from the :prod block of config/runtime.exs (runtime.exs runs in every environment, so outside that block it replaces the development root). A relative path is relative to the current working directory, and in a release the files would go into the release directory and be lost on the next deploy.
• :url_prefix - the path at which the files are served. The default is "/uploads/kotoba". When Kotoba.Storage.Local.Plug serves the files, this is a path, not a full URL: the plug matches requests under it.

Serve the files with Kotoba.Storage.Local.Plug. Any other way to serve them must send X-Content-Type-Options: nosniff, a content type from the allow-list of Kotoba.Attachments, and Content-Disposition: attachment for every type that is not an image, a PDF or a video, as the plug does. A key is always a relative path under the root: a key that Kotoba.Storage.valid_key?/1 refuses gives {:error, :invalid_key}, so a key cannot reach a file outside the root.