Images get lost when moving question to other context

[PhilippImhof]

Description of bug / unexpected behavior

When a question is moved from one context to another, images that are embedded in the part's text get lost.

Expected behavior

The images should still be there, obviously.

How to reproduce the issue

1. Create a new question. Embed an image in the text of part 1. Save the question. Preview the question to verify the image is there.
2. Move the question to another course. (Moving it to a different category of the same course is not enough.)
3. Preview the question again. The image is not there anymore.

The same happens for files embedded in parts' feedback texts.

Additional comments

When moving the files, we use the $questionid:

moodle-qtype_formulas/questiontype.php

Lines 90 to 106 in 32395d9

	public function move_files($questionid, $oldcontextid, $newcontextid) {
	$fs = get_file_storage();
	parent::move_files($questionid, $oldcontextid, $newcontextid);
	$fs->move_area_files_to_new_context($oldcontextid,
	$newcontextid, 'qtype_formulas', 'answersubqtext', $questionid);
	$fs->move_area_files_to_new_context($oldcontextid,
	$newcontextid, 'qtype_formulas', 'answerfeedback', $questionid);
	$fs->move_area_files_to_new_context($oldcontextid,
	$newcontextid, 'qtype_formulas', 'partcorrectfb', $questionid);
	$fs->move_area_files_to_new_context($oldcontextid,
	$newcontextid, 'qtype_formulas', 'partpartiallycorrectfb', $questionid);
	$fs->move_area_files_to_new_context($oldcontextid,
	$newcontextid, 'qtype_formulas', 'partincorrectfb', $questionid);
	$this->move_files_in_combined_feedback($questionid, $oldcontextid, $newcontextid);
	$this->move_files_in_hints($questionid, $oldcontextid, $newcontextid);
	}

However, when saving the question, we use $ans->id which is the part's ID.

moodle-qtype_formulas/questiontype.php

Line 261 in 32395d9

$ans->subqtext = $this->import_or_save_files($subqtextarr, $context, 'qtype_formulas', 'answersubqtext', $ans->id);

[PhilippImhof]

This will be fixed with #62.

[PhilippImhof]

As a side effect, this means that uploaded files (embedded in parts) will not be removed when the question is deleted.