get_oauth2_token clobbered the config's already-resolved token_request_uri
with the AWS template that still contained an unsubstituted account-id
placeholder, so the token exchange POSTed to .../accounts/{}/v1/token. Only
fall back to the AWS endpoint when no token_request_uri is configured.
Co-authored-by: fabian_zse <fabian@zalando.de>
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>