Add offline_access to OIDC standard scopes exclusion list to prevent it
from being incorrectly prefixed, which would break Cognito refresh token
flows. Extract scope transformation into testable _transform_scopes_for_idp()
helper, add debug logging for prefixed scopes, remove unused Settings field
(oauth_routes.py consistently uses os.getenv), and add unit tests.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
When OIDC_RESOURCE_SERVER_ID is set, prefix resource scopes with the
identifier when forwarding to the IdP (e.g., calendar.read becomes
https://example.com/calendar.read). Required for IdPs like AWS Cognito
that mandate {resource_server_id}/{scope} format for custom scopes.
OIDC standard scopes (openid, profile, email) are forwarded as-is.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>