Added check for admin user and test it

Signed-off-by: Marcin Woźniak <y0rune@aol.com>

buisnesslogic/src/main/java/com/plannaplan/services/UserService.java

@@ -85,4 +85,8 @@ public class UserService {
         return this.repo.getByRefreshToken(refreshToken);
     }
 
+    public boolean adminExists(){
+        return this.repo.getAllByRole(UserRoles.ADMIN).size() > 0;
+    } 
+
 }