新增：项目搜索标签删除逻辑

app/controllers/api/v1/project_topics_controller.rb

@@ -24,6 +24,21 @@ class Api::V1::ProjectTopicsController < Api::V1::BaseController
     end
   end
 
+  def destroy 
+    ActiveRecord::Base.transaction do 
+      @project = Project.find_by_id(create_params[:project_id])
+      return render_not_found unless @project.present?
+
+      @project_topic = ProjectTopic.find_by_id(params[:id])
+      @project_topic_ralate = @project_topic.project_topic_ralates.find_by(project_id: @project.id)
+      if @project_topic_ralate.destroy! 
+        render_ok 
+      else 
+        render_error("项目取消关联搜索标签失败.")
+      end
+    end
+  end
+
   private 
   def create_params
     params.permit(:project_id, :name)