public function up(): void 	{ 		Schema::create('client_survey_ppi_questions', function (Blueprint $table): void { 			$table->uuid('id')->primary();  			$table->uuid('client_survey_id')->nullable(); 			$table->uuid('question_id')->nullable();  			$table->foreign('client_survey_id')->references('id')->on('client_surveys')->cascadeOnDelete(); 			$table->foreign('question_id')->references('id')->on('questions')->cascadeOnDelete(); 			$table->timestamps();  			$table->index(Model::CREATED_AT); 		}); 	}