How to register new User in Keycloak over SpringBoot?

How to register/create a new User (Role User) in Keycloak via Spring Boot?

(Register a new User in the provided "Register" Web Page from Keycloak is working)

This is my Controller:

I am able to provide Resources for Entities with the Role User or Admin.

But how can I register, login, logout from Keycloak without using the provided Web Interface (But using Spring Boot)?

@RestController
@RequestMapping("/Hello")
public class HelloController {

   @RequestMapping(value = "/helloWorld", method = RequestMethod.GET)
   public ResponseEntity<String> getHello() {
       return ResponseEntity.ok("Hello World");
   }
   //Only possible with Access Token of an Account which has the Role Admin
   @RolesAllowed("admin")
   @RequestMapping(value = "/admin", method = RequestMethod.GET)
   public ResponseEntity<String> getAdmin(@RequestHeader String Authorization) {
       return ResponseEntity.ok("Hello Admin");
   }
}

This is my application.yml:

server:
 port: 8081
keycloak:
 realm: SpringBootHelloKeycloak
 auth-server-url: http://localhost:8180/auth
 ssl-required: external
 resource: login-app
 credentials:
   secret: c0a68675-8f16-4a13-83dd-6d2111d74ee6
 use-resource-role-mappings: true
 bearer-only: true

Is there any example or any Library for this purpose? Thank you very much in advance