ok  Settings collect Client ID, Client secret, optional Admin API token, and ACST timezone
ok  connection test requires store domain and credentials
ok  token endpoint uses client_credentials against the shop domain
ok  portal obtains an Admin API token and uses it on subsequent requests
ok  cached token is reused until shortly before expiry
ok  expired tokens are renewed automatically
ok  stale Admin API tokens are refreshed and the product sync retried
ok  saving credentials drops the cached token; a pasted Admin API token is used when set
ALL CHECKS PASSED