authenticate
Called by OkHttp whenever a response with HTTP 401 is received.
Inspects the failed request to confirm it was using Bearer authentication, then attempts a single token refresh. Returns the original request (unchanged) so that OkHttp re-runs the application interceptors — io.rekast.sdk.network.interceptor.auth.AccessTokenInterceptor will pick up the new token from CredentialStorage and attach the correct header.
Returns null to give up without retrying in any of the following cases:
The original request did not use Bearer auth.
More than one prior response exists for this request (retry limit reached).
The API key is unavailable (cannot form a Basic Auth token-exchange request).
The product type or subscription key cannot be extracted from the original request.
The Bearer token endpoint itself returns a non-2xx response.
OAuth2 token refresh failure is non-fatal — the original request is still retried with the refreshed Bearer token even if the OAuth2 refresh fails.
Return
The original request to trigger a retry, or null to propagate the 401 to the caller.
Parameters
The route for the failed request (unused but required by the interface).
The 401 response received from the server.