Added @manytoone optional

Author: Rajeev Kumar Singh

src/main/java/com/example/postgresdemo/model/Answer.java

@@ -21,7 +21,7 @@ public class Answer extends AuditModel {
     @Column(columnDefinition = "text")
     private String text;
 
-    @ManyToOne(fetch = FetchType.LAZY)
+    @ManyToOne(fetch = FetchType.LAZY, optional = false)
     @JoinColumn(name = "question_id", nullable = false)
     @OnDelete(action = OnDeleteAction.CASCADE)
     @JsonIgnore