Oauth2.0 Spring Security

I have a question regarding the oauth2.0 openId and spring boot. I am developing a personal project, and I have deployed a Keycloak instance as an Auth server and I am writing code for the resource server. I would like to ask you some questions regarding security. As the Spring Docs say, we need only the issuer-uri of the Auth Server and the Resource Server will use this property to further self-configure, discover the authorization server’s public keys, and subsequently validate incoming JWTs. For example a resource server will have to specify the following:

          issuer-uri: <uri>

However, this means that any resource server can use my deployed Auth Server to self configure just by knowing the issuer-uri is there any way to protect the Auth Server from resource server APIs(that are external to my application)?

Thank you in advance!