refactored RestExceptionHandler

src/main/java/io/zipcoder/tc_spring_poll_application/exception/RestExceptionHandler.java → src/main/java/io/zipcoder/tc_spring_poll_application/dtos/error/RestExceptionHandler.java

-package io.zipcoder.tc_spring_poll_application.exception;
+package io.zipcoder.tc_spring_poll_application.dtos.error;
 
 import io.zipcoder.tc_spring_poll_application.dtos.error.ErrorDetail;
 import io.zipcoder.tc_spring_poll_application.dtos.error.ValidationError;
+import io.zipcoder.tc_spring_poll_application.exception.ResourceNotFoundException;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.MessageSource;
 import org.springframework.context.MessageSourceResolvable;