fix(tag): can not set synonym as tag itself

i18n/en_US.yaml

@@ -109,6 +109,8 @@ backend:
         other: "Should not contain synonym tags."
       cannot_update:
         other: "No permission to update."
+      cannot_set_synonym_as_itself:
+        other: "You cannot set the synonym of the current tag as itself."
     theme:
       not_found:
         other: "Theme not found."

i18n/zh_CN.yaml

@@ -97,6 +97,8 @@ backend:
         other: "不应包含同义词标签。"
       cannot_update:
         other: "没有更新标签权限。"
+      cannot_set_synonym_as_itself:
+        other: "你无法将当前标签的同义词设置为当前标签自己"
     theme:
       not_found:
         other: "主题未找到"

internal/base/reason/reason.go

@@ -58,4 +58,5 @@ const (
 	RevisionReviewUnderway           = "error.revision.review_underway"
 	RevisionNoPermission             = "error.revision.no_permission"
 	UserCannotUpdateYourRole         = "error.user.cannot_update_your_role"
+	TagCannotSetSynonymAsItself      = "error.tag.cannot_set_synonym_as_itself"
 )

internal/service/tag/tag_service.go

@@ -216,6 +216,9 @@ func (ts *TagService) UpdateTagSynonym(ctx context.Context, req *schema.UpdateTa
 
 	// find all exist tag
 	for _, item := range req.SynonymTagList {
+		if item.SlugName == mainTagInfo.SlugName {
+			return errors.BadRequest(reason.TagCannotSetSynonymAsItself)
+		}
 		addSynonymTagList = append(addSynonymTagList, item.SlugName)
 	}
 	tagListInDB, err := ts.tagCommonService.GetTagListByNames(ctx, addSynonymTagList)