[Feat]: 닉네임 변경 API 구현

src/main/java/io/sobok/SobokSobok/auth/application/UserService.java

@@ -7,6 +7,9 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
+
+import io.sobok.SobokSobok.exception.ErrorCode;
+import io.sobok.SobokSobok.exception.model.ConflictException;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
@@ -42,4 +45,16 @@ public List<UsernameResponse> getUsername(Long userId, String username) {
 
         return result;
     }
+
+    @Transactional
+    public void changeUsername(Long userId, String username) {
+
+        User user = UserServiceUtil.findUserById(userRepository, userId);
+
+        if (duplicateNickname(username)) {
+            throw new ConflictException(ErrorCode.ALREADY_USING_USERNAME);
+        }
+
+        user.changeUsername(username);
+    }
 }

src/main/java/io/sobok/SobokSobok/auth/domain/User.java

@@ -58,6 +58,10 @@ public void updateDeviceToken(String newDeviceToken) {
         this.deviceToken = newDeviceToken;
     }
 
+    public void changeUsername(String username) {
+        this.username = username;
+    }
+
     public void deleteUser() {
         this.deviceToken = "";
         this.username = "";

src/main/java/io/sobok/SobokSobok/auth/ui/UserController.java

@@ -2,12 +2,15 @@
 
 import io.sobok.SobokSobok.auth.application.UserService;
 import io.sobok.SobokSobok.auth.domain.User;
+import io.sobok.SobokSobok.auth.ui.dto.UsernameRequest;
 import io.sobok.SobokSobok.auth.ui.dto.UsernameResponse;
 import io.sobok.SobokSobok.common.dto.ApiResponse;
 import io.sobok.SobokSobok.exception.SuccessCode;
 import io.swagger.v3.oas.annotations.Operation;
 import io.swagger.v3.oas.annotations.tags.Tag;
 import java.util.List;
+
+import jakarta.validation.Valid;
 import lombok.RequiredArgsConstructor;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
@@ -53,4 +56,22 @@ public ResponseEntity<ApiResponse<List<UsernameResponse>>> getUsername(
                 userService.getUsername(user.getId(), username)
             ));
     }
+
+    @PutMapping("/nickname")
+    @Operation(
+            summary = "유저 닉네임 변경 API 메서드",
+            description = "유저 본인의 닉네임을 변경하는 메서드입니다."
+    )
+    public ResponseEntity<ApiResponse<Void>> changeUsername(
+            @AuthenticationPrincipal User user,
+            @RequestBody @Valid final UsernameRequest request
+    ) {
+
+        userService.changeUsername(user.getId(), request.username());
+        return ResponseEntity
+                .status(HttpStatus.OK)
+                .body(ApiResponse.success(
+                        SuccessCode.CHANGE_NICKNAME_SUCCESS
+                ));
+    }
 }

src/main/java/io/sobok/SobokSobok/auth/ui/dto/UsernameRequest.java

@@ -0,0 +1,10 @@
+package io.sobok.SobokSobok.auth.ui.dto;
+
+import jakarta.validation.constraints.NotBlank;
+
+public record UsernameRequest(
+
+        @NotBlank
+        String username
+) {
+}

src/main/java/io/sobok/SobokSobok/exception/SuccessCode.java

@@ -17,6 +17,7 @@ public enum SuccessCode {
 
     // user
     NICKNAME_CHECK_SUCCESS(HttpStatus.OK, "닉네임 중복 확인에 성공했습니다."),
+    CHANGE_NICKNAME_SUCCESS(HttpStatus.OK, "닉네임 변경에 성공했습니다."),
     GET_USERNAME_SUCCESS(HttpStatus.OK, "유저 이름 조회에 성공했습니다."),
 
     // pill