feat(relation): 实现用户关注功能

- 新增关注用户接口，支持通过用户ID关注其他用户
- 添加参数校验，确保被关注用户ID不为空
- 实现关注用户时的业务逻辑，包括：
  -不能关注自己
  - 校验被关注用户是否存
  - 集成Feign客户端，调用用户服务查询用户信息
- 定义关注相关的异常码和错误信息
- 更新网关配置，路由/relation/**请求到用户关系服务- 添加HTTP客户端测试用例，用于验证关注功能
- 引入用户API依赖，支持远程调用用户服务

han-note-user-relation/han-note-user-relation-biz/src/main/java/com/hanserwei/hannote/user/relation/biz/HannoteUserRelationBizApplication.java

@@ -3,9 +3,11 @@ package com.hanserwei.hannote.user.relation.biz;
 import org.mybatis.spring.annotation.MapperScan;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.cloud.openfeign.EnableFeignClients;
 
 @SpringBootApplication
 @MapperScan("com.hanserwei.hannote.user.relation.biz.domain.mapper")
+@EnableFeignClients(basePackages = "com.hanserwei.hannote")
 public class HannoteUserRelationBizApplication {
     public static void main(String[] args) {
         SpringApplication.run(HannoteUserRelationBizApplication.class, args);

han-note-user-relation/han-note-user-relation-biz/src/main/java/com/hanserwei/hannote/user/relation/biz/controller/RelationController.java

@@ -0,0 +1,29 @@
+package com.hanserwei.hannote.user.relation.biz.controller;
+
+import com.hanserwei.framework.biz.operationlog.aspect.ApiOperationLog;
+import com.hanserwei.framework.common.response.Response;
+import com.hanserwei.hannote.user.relation.biz.model.vo.FollowUserReqVO;
+import com.hanserwei.hannote.user.relation.biz.service.RelationService;
+import jakarta.annotation.Resource;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.validation.annotation.Validated;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+@RequestMapping("/relation")
+@Slf4j
+public class RelationController {
+
+    @Resource
+    private RelationService relationService;
+
+    @PostMapping("/follow")
+    @ApiOperationLog(description = "关注用户")
+    public Response<?> follow(@Validated @RequestBody FollowUserReqVO followUserReqVO) {
+        return relationService.follow(followUserReqVO);
+    }
+
+}

han-note-user-relation/han-note-user-relation-biz/src/main/java/com/hanserwei/hannote/user/relation/biz/enums/ResponseCodeEnum.java

@@ -13,6 +13,8 @@ public enum ResponseCodeEnum implements BaseExceptionInterface {
     PARAM_NOT_VALID("RELATION-10001", "参数错误"),
 
     // ----------- 业务异常状态码 -----------
+    CANT_FOLLOW_YOUR_SELF("RELATION-20001", "无法关注自己"),
+    FOLLOW_USER_NOT_EXISTED("RELATION-20002", "关注的用户不存在"),
     ;
 
     // 异常码

han-note-user-relation/han-note-user-relation-biz/src/main/java/com/hanserwei/hannote/user/relation/biz/model/vo/FollowUserReqVO.java

@@ -0,0 +1,17 @@
+package com.hanserwei.hannote.user.relation.biz.model.vo;
+
+import jakarta.validation.constraints.NotNull;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+@Data
+@AllArgsConstructor
+@NoArgsConstructor
+@Builder
+public class FollowUserReqVO {
+
+    @NotNull(message = "被关注用户 ID 不能为空")
+    private Long followUserId;
+}

han-note-user-relation/han-note-user-relation-biz/src/main/java/com/hanserwei/hannote/user/relation/biz/rpc/UserRpcService.java

@@ -0,0 +1,37 @@
+package com.hanserwei.hannote.user.relation.biz.rpc;
+
+import com.hanserwei.framework.common.response.Response;
+import com.hanserwei.hannote.user.api.UserFeignApi;
+import com.hanserwei.hannote.user.dto.req.FindUserByIdReqDTO;
+import com.hanserwei.hannote.user.dto.resp.FindUserByIdRspDTO;
+import jakarta.annotation.Resource;
+import org.springframework.stereotype.Component;
+
+import java.util.Objects;
+
+@Component
+public class UserRpcService {
+
+    @Resource
+    private UserFeignApi userFeignApi;
+
+    /**
+     * 根据用户 ID 查询
+     *
+     * @param userId 用户 ID
+     * @return 用户信息
+     */
+    public FindUserByIdRspDTO findById(Long userId) {
+        FindUserByIdReqDTO findUserByIdReqDTO = new FindUserByIdReqDTO();
+        findUserByIdReqDTO.setId(userId);
+
+        Response<FindUserByIdRspDTO> response = userFeignApi.findById(findUserByIdReqDTO);
+
+        if (!response.isSuccess() || Objects.isNull(response.getData())) {
+            return null;
+        }
+
+        return response.getData();
+    }
+
+}

han-note-user-relation/han-note-user-relation-biz/src/main/java/com/hanserwei/hannote/user/relation/biz/service/RelationService.java

@@ -0,0 +1,15 @@
+package com.hanserwei.hannote.user.relation.biz.service;
+
+import com.hanserwei.framework.common.response.Response;
+import com.hanserwei.hannote.user.relation.biz.model.vo.FollowUserReqVO;
+
+public interface RelationService {
+
+    /**
+     * 关注用户
+     *
+     * @param followUserReqVO 关注用户请求
+     * @return 响应
+     */
+    Response<?> follow(FollowUserReqVO followUserReqVO);
+}

han-note-user-relation/han-note-user-relation-biz/src/main/java/com/hanserwei/hannote/user/relation/biz/service/impl/RelationServiceImpl.java

@@ -0,0 +1,48 @@
+package com.hanserwei.hannote.user.relation.biz.service.impl;
+
+import com.hanserwei.framework.biz.context.holder.LoginUserContextHolder;
+import com.hanserwei.framework.common.exception.ApiException;
+import com.hanserwei.framework.common.response.Response;
+import com.hanserwei.hannote.user.dto.resp.FindUserByIdRspDTO;
+import com.hanserwei.hannote.user.relation.biz.enums.ResponseCodeEnum;
+import com.hanserwei.hannote.user.relation.biz.model.vo.FollowUserReqVO;
+import com.hanserwei.hannote.user.relation.biz.rpc.UserRpcService;
+import com.hanserwei.hannote.user.relation.biz.service.RelationService;
+import jakarta.annotation.Resource;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Service;
+
+import java.util.Objects;
+
+@Service
+@Slf4j
+public class RelationServiceImpl implements RelationService {
+
+    @Resource
+    private UserRpcService userRpcService;
+
+    @Override
+    public Response<?> follow(FollowUserReqVO followUserReqVO) {
+        // 获取被关注用户 ID
+        Long followUserId = followUserReqVO.getFollowUserId();
+
+        // 获取当前登录用户 ID
+        Long userId = LoginUserContextHolder.getUserId();
+        if (Objects.equals(userId, followUserId)) {
+            throw new ApiException(ResponseCodeEnum.CANT_FOLLOW_YOUR_SELF);
+        }
+        // 校验关注的用户是否存在
+        FindUserByIdRspDTO findUserByIdRspDTO = userRpcService.findById(followUserId);
+        if (Objects.isNull(findUserByIdRspDTO)){
+            throw new ApiException(ResponseCodeEnum.FOLLOW_USER_NOT_EXISTED);
+        }
+
+        // TODO: 校验关注数是否已经达到上限
+
+        // TODO: 写入 Redis ZSET 关注列表
+
+        // TODO: 发送 MQ
+
+        return Response.success();
+    }
+}