realm
Specifies the authentication realm this provider should answer.
The realm is matched against the realm parameter from a WWW-Authenticate: Bearer challenge. Leave it null (default) when the client has a single bearer provider or when the server does not distinguish bearer credentials by realm. Set it when multiple bearer providers are installed, and this provider should only handle challenges for a particular protection space.
Typical values are the exact realm strings advertised by the server, for example api, admin, or another application-defined name. Do not include the Bearer scheme name. When set, a bearer challenge whose realm parameter is absent or different is ignored by this provider.