made changes in classes and methods to make frontend and backend work together

made changes to the model classes, removed abstract class question and made it usable for all question types. added QuestionType enum

FullstackProsjekt/src/backend/main/java/edu/ntnu/idatt2105/configuration/CorsConfig.java

@@ -9,7 +9,7 @@ public class CorsConfig implements WebMvcConfigurer {
   @Override
   public void addCorsMappings(CorsRegistry registry) {
     registry.addMapping("/**")
-        .allowedOrigins("http://localhost:4173")
+        .allowedOrigins("http://localhost:5173")
         .allowedMethods("GET", "POST", "PUT", "DELETE")
         .allowedHeaders("*");
   }