Retrieve the configurable reasons defined in Settings -> Customizations (denial, withdrawal, write-off, and adjustment reasons). Use this to discover the valid values for filters such as the Communication Template withdrawalReasons field. Authentication: requires an OAuth2 client-credentials Bearer token whose client holds the reasons scope (Permission: Read Reasons). The Accept: application/vnd.totality.v1+json header is required on every request (it selects the API version); requests sent without it are treated as browser requests and redirected to the login page instead of returning JSON.