Api/QuestionController: improve updating of answerChoices

[schu]

openmultiplechoice/app/Http/Controllers/Api/QuestionController.php

Lines 54 to 60 in 5444f30

	// Update all answer choices for this question as the correct
	// answer could have been changed
	$answerChoices = AnswerChoice::where('question_id', '=', $question->id)->get();
	foreach ($answerChoices as $answerChoice) {
	$answerChoice->is_correct = $answerChoice->answer_id == $question->correct_answer_id;
	$answerChoice->save();
	}

This can quickly be thousands of objects and updates for frequently answered questions. Instead, use a query and let the database do the work.