Add API error class to handle API error message

app/controllers/api/v1/api_controller.rb

@@ -6,7 +6,8 @@ class ApiController < ApplicationController
       skip_before_action :verify_authenticity_token
 
       rescue_from ActiveRecord::RecordNotUnique do
-        render json: {error: "RecordNotUnique", message: t("error.already_in_playlist")}, status: :bad_request
+        # render json: {type: "RecordNotUnique", message: t("error.already_in_playlist")}, status: :bad_request
+        render json: ApiError.new(:record_not_unique, t("error.already_in_playlist")), status: :bad_request
       end
 
       private

app/models/api_error.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+class ApiError
+  TYPES = {
+    record_not_unique: "RecordNotUnique"
+  }
+
+  attr_reader :type, :message
+
+  def initialize(type_key, message)
+    @type = TYPES[type_key]
+    @message = message
+  end
+
+  def to_json(*_args)
+    {type: @type, message: @message}.to_json
+  end
+end

test/controllers/api/v1/current_playlist/songs_controller_test.rb

@@ -69,7 +69,7 @@ class Api::V1::CurrentPlaylist::SongsControllerTest < ActionDispatch::Integratio
     response = @response.parsed_body
 
     assert_response :bad_request
-    assert_equal "RecordNotUnique", response["error"]
+    assert_equal "RecordNotUnique", response["type"]
     assert_not_empty response["message"]
   end
 end

test/controllers/api/v1/favorite_playlist/songs_controller_test.rb

@@ -25,7 +25,7 @@ class Api::V1::FavoritePlaylist::SongsControllerTest < ActionDispatch::Integrati
     response = @response.parsed_body
 
     assert_response :bad_request
-    assert_equal "RecordNotUnique", response["error"]
+    assert_equal "RecordNotUnique", response["type"]
     assert_not_empty response["message"]
   end
 end