Returns a specification to start this module under a supervisor.

See Supervisor.

@spec refresh_keys() :: :ok

Asynchronously queues a key refresh.

Fire-and-forget cast; returns :ok immediately without waiting for the fetch to complete. Intended for internal use by the scheduled-refresh timer — callers that need to know whether the refresh succeeded should use refresh_now/0 instead.

@spec start_link(keyword()) :: GenServer.on_start()

Starts the key store GenServer and registers it under this module's name.

Options:

• :refresh_interval — fallback interval, in milliseconds, between background refreshes when Google's Cache-Control: max-age header is missing or unparseable. Defaults to 30 minutes.
• :url — JWKS endpoint to fetch. Defaults to Google's public key URL; overridable primarily for tests.

Typically started by the library's application supervisor — host applications do not need to invoke this directly.