Adding Schema example for swagger

application/model/src/main/java/org/fuseri/model/dto/certificate/CertificateCreateDto.java

 package org.fuseri.model.dto.certificate;
 
+import io.swagger.v3.oas.annotations.media.Schema;
 import jakarta.validation.Valid;
 import jakarta.validation.constraints.NotNull;
 import lombok.Getter;
@@ -12,6 +13,36 @@ import org.fuseri.model.dto.user.UserDto;
  * This class represents a Data Transfer Object (DTO) for creating Certificate entities.
  * It is used for creating Certificate entity.
  */
+@Schema(example = """
+        {
+           "user": {
+                   "id": 1,
+                   "username": "adelkaxxx",
+                   "email": "adelkaxxx@muni.mail.cz",
+                   "firstName": "Adéla",
+                   "lastName": "Pulcová",
+                   "address": {
+                     "country": "Czechia",
+                     "city": "Praha",
+                     "street": "Bubenské nábřeží",
+                     "houseNumber": "306/13",
+                     "zip": "170 00"
+                   },
+                   "userType": "STUDENT",
+                   "languageProficiency": {
+                     "CZECH": "A2"
+                   }
+                 },
+           "course": {
+                   "id": 1,
+                   "name": "english a1",
+                   "capacity": 10,
+                   "language": "ENGLISH",
+                   "proficiency": "A1"
+                 }
+         
+         }
+        """)
 @Getter
 @Setter
 public class CertificateCreateDto {