Add Answer validation

application/model/src/main/java/org/fuseri/model/dto/exercise/AnswerCreateDto.java

 package org.fuseri.model.dto.exercise;
 
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.NotNull;
 import lombok.AllArgsConstructor;
 import lombok.Getter;
 
 @AllArgsConstructor
 @Getter
 public class AnswerCreateDto {
+
+    @NotBlank
     private String text;
+
+    @NotNull
     private boolean correct;
+
+    @NotBlank
     private String questionId;
 }

application/model/src/main/java/org/fuseri/model/dto/exercise/AnswerDto.java

 package org.fuseri.model.dto.exercise;
 
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.NotNull;
 import lombok.AllArgsConstructor;
 import lombok.Getter;
 import org.fuseri.model.dto.common.DomainObjectDto;
@@ -7,6 +9,10 @@ import org.fuseri.model.dto.common.DomainObjectDto;
 @AllArgsConstructor
 @Getter
 public class AnswerDto extends DomainObjectDto {
+
+    @NotBlank
     private String text;
+
+    @NotNull
     private boolean correct;
 }

application/model/src/main/java/org/fuseri/model/dto/exercise/AnswerInQuestionCreateDto.java

 package org.fuseri.model.dto.exercise;
 
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.NotNull;
 import lombok.AllArgsConstructor;
 import lombok.Getter;
 
 @AllArgsConstructor
 @Getter
 public class AnswerInQuestionCreateDto {
+
+    @NotBlank
     private String text;
+
+    @NotNull
     private boolean correct;
 }

application/model/src/main/java/org/fuseri/model/dto/exercise/AnswersCreateDto.java

 package org.fuseri.model.dto.exercise;
 
+import jakarta.validation.Valid;
+import jakarta.validation.constraints.NotBlank;
 import lombok.AllArgsConstructor;
 import lombok.Getter;
 
@@ -8,6 +10,10 @@ import java.util.List;
 @AllArgsConstructor
 @Getter
 public class AnswersCreateDto {
+
+    @NotBlank
     private String questionId;
+
+    @Valid
     private List<AnswerInQuestionCreateDto> answers;
 }

application/module-exercise/src/main/java/org/fuseri/moduleexercise/answer/AnswerController.java

 package org.fuseri.moduleexercise.answer;
 
 import jakarta.persistence.EntityNotFoundException;
+import jakarta.validation.Valid;
+import jakarta.validation.constraints.NotBlank;
 import org.fuseri.model.dto.exercise.AnswerCreateDto;
 import org.fuseri.model.dto.exercise.AnswerDto;
 import org.fuseri.model.dto.exercise.AnswersCreateDto;
@@ -33,7 +35,7 @@ public class AnswerController {
      * @return a List of AnswerDto objects
      */
     @GetMapping("/{question-id}")
-    public List<AnswerDto> findAllByQuestionId(@PathVariable("question-id") String questionId) {
+    public List<AnswerDto> findAllByQuestionId(@NotBlank @PathVariable("question-id") String questionId) {
         return facade.findAllByQuestionId(questionId);
     }
 
@@ -45,7 +47,7 @@ public class AnswerController {
      * @throws ResponseStatusException if the question ID specified in the dto does not exist
      */
     @PostMapping
-    public List<AnswerDto> createMultiple(@RequestBody AnswersCreateDto dto) {
+    public List<AnswerDto> createMultiple(@Valid @RequestBody AnswersCreateDto dto) {
         try {
             return facade.createMultiple(dto);
         } catch (EntityNotFoundException e) {
@@ -61,7 +63,7 @@ public class AnswerController {
      * @throws ResponseStatusException if the question id specified in the AnswerCreateDto dto does not exist
      */
     @PutMapping("/{id}")
-    public AnswerDto update(@PathVariable String id, @RequestBody AnswerCreateDto dto) {
+    public AnswerDto update(@NotBlank @PathVariable String id, @Valid @RequestBody AnswerCreateDto dto) {
         try {
             return facade.update(id, dto);
         } catch (EntityNotFoundException e) {
@@ -77,7 +79,7 @@ public class AnswerController {
      * @throws ResponseStatusException if answer with specified id does not exist
      */
     @DeleteMapping("/{id}")
-    public void delete(@PathVariable String id) {
+    public void delete(@NotBlank @PathVariable String id) {
         try {
             facade.delete(id);
         } catch (EntityNotFoundException e) {