NCP-2 add logout

src/main/java/ru/soune/no_copy/service/AuthService.java

@@ -78,6 +78,10 @@ public class AuthService {
         return authTokenRepository.save(authToken);
     }
 
+    public void logout(String token) {
+        authTokenRepository.findByToken(token)
+                .ifPresent(authTokenRepository::delete);
+    }
 
     private String generateAuthToken() {
         byte[] bytes = new byte[32];