ConstReadonlyApp: 10The application's own settings. The default.
ReadonlyModule: 20Settings contributed by a module, layered on top of the application's.
ReadonlySources: 0Remote and external sources (SSM, Secrets Manager, files): everything else may depend on them.
Named execution steps for ConfigurationOptions.priority.
The gaps are deliberate: they leave room to slot a configuration between two steps without renumbering anything.