Plug that serves session files over HTTP with signed token authorization.
Mount in your router with forward:
forward "/omni_files", Omni.UI.Files.PlugFile URLs use signed tokens that encode the session ID, so only the
LiveView that created the token can authorize access to a session's files.
Tokens are generated via Omni.UI.Files.URL.file_url/3.
URL format
GET /omni_files/{token}/{filename}Options
:max_age— maximum token age in seconds (default: 86400 = 24 hours)