[#152] Remove pluginfile tokens

[owenherbert-catalyst]

Issue: #152

This PR improves handling of @@PLUGINFILE@@ tokens in search snippets and updates the associated PHPUnit tests.

Steps to reproduce and test:

1. Install a 4.5 Moodle locally

git clone -b MOODLE_405_STABLE git@github.com:moodle/moodle.git moodle405stable
cd $DOCKER_DEV_ROOT/sites/moodle405stable
git clean -ffd && git submodule sync && git submodule update --init --recursive --force --jobs 16
control add moodle405stable --db pgsql --php 8.3 --elasticsearch
control install moodle405stable --adminuser admin --adminpass admin

2. Install elastic search plugin https://github.com/mattporritt/moodle-search_elastic (MOODLE_404_STABLE)
3. Create a new course named "test"
4. Add a file to the course named "test", set description to "@@PluginFile@@/image.png", select a random file
5. Save and display
6. Go to /admin/searchareas.php, reindex courses search area
7. Go to /admin/searchareas.php, reindex images search area
8. Go to /admin/tool/task/scheduledtasks.php, run "Global search indexing" task
9. Go to /search/index.php, search for "test". Obersve the warning
10. Update the moodle-search_elastic plugin to use the feature branch owenherbert-catalyst:issue-152-fix
11. Repeat step 9, observe the warning is gone.

[dmitriim]

@owenherbert-catalyst , do I understand this correctly? We remove the token because there is no way to reconstruct the full plugin file URL?

I'm also wondering what the real-world use case is for reproducing this issue. The testing instructions seem to rely on a fairly artificial scenario.

[owenherbert-catalyst]

Hey @dmitriim , I created a core tracker for this a while ago. This can be seen here. This issue can be reproduced in all search plugins not just Elastic search.

I believe the more correct approach is to address it in core.

[dmitriim]

Yes. That was my thought. I think we should close this PR and instead fix it in core.