added endpoints to backend

created endpoints and crud-operations for these endpoints.

src/main/java/ntnu/idatt2105/group44/trivioServer/advice/TrivioNotFoundAdvice.java

+package ntnu.idatt2105.group44.trivioServer.advice;
+
+import ntnu.idatt2105.group44.trivioServer.exception.TrivioNotFoundException;
+import org.springframework.http.HttpStatus;
+import org.springframework.web.bind.annotation.ControllerAdvice;
+import org.springframework.web.bind.annotation.ExceptionHandler;
+import org.springframework.web.bind.annotation.ResponseStatus;
+
+@ControllerAdvice
+public class TrivioNotFoundAdvice {
+
+  @ExceptionHandler
+  @ResponseStatus(HttpStatus.NOT_FOUND)
+  String TrivioNotFoundHandler(TrivioNotFoundException ex) {
+    return ex.getMessage();
+  }
+}