is this table is correct? or i should put unsignedBigInteger for tag_id too? and remove.->unsigned and index? :  /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('post_tags', function (Blueprint $table) {
            $table->unsignedBigInteger('post_id');
            $table->integer('tag_id')->unsigned()->index();
            $table->foreign('post_id')->references('id')->on('posts')->onDelete('cascade');
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('post_tags');
    }