fixes serialization issue with enrollment class.

[stopfstedt]

Running Moodle-core test coverage with this enrollment plugin integrated causes several failures, all with a Exception: Serialization of 'Closure' is not allowed.

Here is one example:

stefan@nichtsnutz: ~/dev/projects/moodle44 on MOODLE_404_STABLE[?]
$ vendor/bin/phpunit --filter=test_data_saved admin/tool/uploadcourse/tests/course_test.php
Moodle 4.4.4+ (Build: 20241101), 99b5729824524e0bdc6a64ff1b0e4423d1d4b37a
Php: 8.3.13, mysqli: 8.0.39, OS: Linux 6.8.0-48-generic x86_64
PHPUnit 9.6.18 by Sebastian Bergmann and contributors.

E                                                                   1 / 1 (100%)

Time: 00:44.495, Memory: 82.50 MB

There was 1 error:

1) tool_uploadcourse\course_test::test_data_saved
Exception: Serialization of 'Closure' is not allowed

/home/stefan/dev/projects/moodle44/cache/stores/static/lib.php:243
/home/stefan/dev/projects/moodle44/cache/stores/static/lib.php:338
/home/stefan/dev/projects/moodle44/cache/classes/loaders.php:903
/home/stefan/dev/projects/moodle44/cache/classes/loaders.php:826
/home/stefan/dev/projects/moodle44/admin/tool/uploadcourse/classes/helper.php:184
/home/stefan/dev/projects/moodle44/admin/tool/uploadcourse/classes/helper.php:161
/home/stefan/dev/projects/moodle44/admin/tool/uploadcourse/classes/course.php:821
/home/stefan/dev/projects/moodle44/admin/tool/uploadcourse/tests/course_test.php:535
/home/stefan/dev/projects/moodle44/lib/phpunit/classes/advanced_testcase.php:76

ERRORS!
Tests: 1, Assertions: 5, Errors: 1.

Using a step-through debugger, I was able to pinpoint the problem - the Ilios API client cannot be set as class member during serialization, since brings in closures of the underlying HTTP client (Guzzle).

See screenshot below with highlighted closures:

I'm side-stepping this issue by getting the client inside the only function that's actually using it. that get's around this problem since the methods in an object will not be saved, only the name of the class.

after the change/for comparison:

[jrjohnson]

Simple, works. ✅