feat: Applicant 도메인 구현

* feat: Applicant (지원자) 도메인 초기 구현
- 지원자 엔티티 구현, 등록 요청 DTO 구현
- ApplicantStatus Enum으로 지원자 상태 관리

* feat: 제약조건 위반 예외 핸들러 메소드 추가

* feat: 지원자 상태 변경 메소드 추가

Author: ysw789

src/main/java/dmu/dasom/api/domain/applicant/dto/ApplicantCreateRequestDto.java

@@ -0,0 +1,61 @@
+package dmu.dasom.api.domain.applicant.dto;
+
+import dmu.dasom.api.domain.applicant.entity.Applicant;
+import io.swagger.v3.oas.annotations.media.Schema;
+import jakarta.validation.constraints.*;
+import lombok.Getter;
+
+@Getter
+@Schema(name = "ApplicantCreateRequestDto", description = "지원자 생성 요청 DTO")
+public class ApplicantCreateRequestDto {
+
+    @NotNull
+    @Pattern(regexp = "^[0-9]{8}$")
+    @Size(min = 8, max = 8)
+    @Schema(description = "학번", example = "20231234")
+    private String studentNo;
+
+    @NotNull
+    @Pattern(regexp = "^\\d{3}-\\d{4}-\\d{4}$")
+    @Size(min = 13, max = 13)
+    @Schema(description = "연락처", example = "010-1234-5678")
+    private String contact;
+
+    @Email
+    @NotNull
+    @Size(max = 64)
+    @Schema(description = "이메일 주소", example = "[email protected]")
+    private String email;
+
+    @Min(value = 1)
+    @Max(value = 4)
+    @NotNull
+    @Schema(description = "학년", example = "3")
+    private Integer grade;
+
+    @NotNull
+    @Size(max = 500)
+    @Schema(description = "지원 동기", example = "동아리 활동에 관심이 있어서 지원합니다.")
+    private String reasonForApply;
+
+    @Size(max = 200)
+    @Schema(description = "활동 희망사항", example = "동아리 활동 참여")
+    private String activityWish;
+
+    @NotNull
+    @Schema(description = "개인정보 처리방침 동의 여부", example = "true")
+    private Boolean isPrivacyPolicyAgreed;
+
+    public Applicant toEntity() {
+        return Applicant.builder()
+                .studentNo(this.studentNo)
+                .contact(this.contact)
+                .email(this.email)
+                .grade(this.grade)
+                .reasonForApply(this.reasonForApply)
+                .activityWish(this.activityWish)
+                .isPrivacyPolicyAgreed(this.isPrivacyPolicyAgreed)
+                .build();
+    }
+
+}

src/main/java/dmu/dasom/api/domain/applicant/entity/Applicant.java

@@ -0,0 +1,76 @@
+package dmu.dasom.api.domain.applicant.entity;
+
+import dmu.dasom.api.domain.applicant.enums.ApplicantStatus;
+import jakarta.persistence.*;
+import jakarta.validation.constraints.*;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import org.springframework.data.annotation.CreatedDate;
+import org.springframework.data.annotation.LastModifiedDate;
+import org.springframework.data.jpa.domain.support.AuditingEntityListener;
+
+import java.time.LocalDateTime;
+
+@AllArgsConstructor
+@Builder
+@Entity
+@EntityListeners(AuditingEntityListener.class)
+@Getter
+@NoArgsConstructor
+public class Applicant {
+
+    @Column(name = "id")
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    @Id
+    private Long id;
+
+    @Column(name = "student_no", nullable = false, length = 8)
+    @Pattern(regexp = "^[0-9]{8}$")
+    @Size(min = 8, max = 8)
+    private String studentNo;
+
+    @Column(name = "contact", nullable = false, length = 13)
+    @Pattern(regexp = "^\\d{3}-\\d{4}-\\d{4}$")
+    @Size(min = 13, max = 13)
+    private String contact;
+
+    @Column(name = "email", nullable = false, length = 64)
+    @Email
+    @Size(max = 64)
+    private String email;
+
+    @Column(name = "grade", nullable = false)
+    @Min(1) @Max(4)
+    private int grade;
+
+    @Column(name = "reason_for_apply", nullable = false, length = 500)
+    @Size(max = 500)
+    private String reasonForApply;
+
+    @Column(name = "activity_wish", nullable = true, length = 200)
+    @Size(max = 200)
+    private String activityWish;
+
+    @Column(name = "is_privacy_policy_agreed", nullable = false)
+    private Boolean isPrivacyPolicyAgreed;
+
+    @Builder.Default
+    @Column(name = "status", nullable = false, length = 16)
+    @Enumerated(EnumType.STRING)
+    private ApplicantStatus status = ApplicantStatus.PENDING;
+
+    @CreatedDate
+    @Column(name = "created_at", nullable = false, updatable = false)
+    private LocalDateTime createdAt;
+
+    @Column(name = "updated_at", nullable = false)
+    @LastModifiedDate
+    private LocalDateTime updatedAt;
+
+    public void updateStatus(final ApplicantStatus status) {
+        this.status = status;
+    }
+
+}

src/main/java/dmu/dasom/api/domain/applicant/enums/ApplicantStatus.java

@@ -0,0 +1,9 @@
+package dmu.dasom.api.domain.applicant.enums;
+
+public enum ApplicantStatus {
+    PENDING,             // 초기 상태
+    DOCUMENT_FAILED,     // 서류 심사 불합격
+    DOCUMENT_PASSED,     // 서류 심사 합격
+    INTERVIEW_FAILED,    // 면접 불합격
+    INTERVIEW_PASSED     // 면접 합격
+}

src/main/java/dmu/dasom/api/domain/applicant/repository/ApplicantRepository.java

@@ -0,0 +1,7 @@
+package dmu.dasom.api.domain.applicant.repository;
+
+import dmu.dasom.api.domain.applicant.entity.Applicant;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+public interface ApplicantRepository extends JpaRepository<Applicant, Long> {
+}

src/main/java/dmu/dasom/api/domain/applicant/service/ApplicantService.java

@@ -0,0 +1,9 @@
+package dmu.dasom.api.domain.applicant.service;
+
+import dmu.dasom.api.domain.applicant.dto.ApplicantCreateRequestDto;
+
+public interface ApplicantService {
+
+    void apply(final ApplicantCreateRequestDto request);
+
+}

src/main/java/dmu/dasom/api/domain/applicant/service/ApplicantServiceImpl.java

@@ -0,0 +1,20 @@
+package dmu.dasom.api.domain.applicant.service;
+
+import dmu.dasom.api.domain.applicant.dto.ApplicantCreateRequestDto;
+import dmu.dasom.api.domain.applicant.repository.ApplicantRepository;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+
+@RequiredArgsConstructor
+@Service
+public class ApplicantServiceImpl implements ApplicantService {
+
+    private final ApplicantRepository applicantRepository;
+
+    // 지원자 저장
+    @Override
+    public void apply(final ApplicantCreateRequestDto request) {
+        applicantRepository.save(request.toEntity());
+    }
+
+}

src/main/java/dmu/dasom/api/domain/common/exception/CustomControllerAdvice.java

@@ -1,5 +1,6 @@
 package dmu.dasom.api.domain.common.exception;
 
+import jakarta.validation.ConstraintViolationException;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.MethodArgumentNotValidException;
@@ -19,4 +20,9 @@ public ResponseEntity<ErrorResponse> methodArgumentNotValidException(final Metho
         return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(new ErrorResponse(ErrorCode.ARGUMENT_NOT_VALID));
     }
 
+    @ExceptionHandler(ConstraintViolationException.class)
+    public ResponseEntity<ErrorResponse> constraintViolationException(final ConstraintViolationException e) {
+        return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(new ErrorResponse(ErrorCode.ARGUMENT_NOT_VALID));
+    }
+
 }