Allow additional users to manage students

[donnapep]

Part of https://github.com/Automattic/sensei-pro/issues/2618.

Proposed Changes

Add a filter to allow additional users to manage students (admins and teacher are the default).

Instead of using a hook, I debated changing the manage_sensei check to manage_sensei_grades, but this cap feels like it should be restricted to the Grading menu based on its naming. Perhaps we could consider adding a new one for student management in the future?

I was only able to add a couple of test cases, as most of the functions that were changed call exit, so I tested the use cases where return is called before an exit.

Testing Instructions

See https://github.com/Automattic/sensei-pro/pull/2619.

New/Updated Hooks

• sensei_learners_allowed_user_ids - Filter the user IDs that have permission to manage students.

Pre-Merge Checklist

• PR title and description contain sufficient detail and accurately describe the changes
• Acceptance criteria is met
• Decisions are publicly documented
• Adheres to coding standards (PHP, JavaScript, CSS, HTML)
• All strings are translatable (without concatenation, handles plurals)
• Follows our naming conventions (P6rkRX-4oA-p2)
• Hooks (p6rkRX-1uS-p2) and functions are documented
• New UIs are responsive and use a mobile-first approach
• New UIs match the designs
• Different user privileges (admin, teacher, subscriber) are tested as appropriate
• Legacy courses (course without blocks) are tested
• Code is tested on the minimum supported PHP and WordPress versions
• User interface changes have been tested on the latest versions of Chrome, Firefox and Safari
• "Needs Documentation" label is added if this change requires updates to documentation
• Known issues are created as new GitHub issues

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[m1r0]

Looks good overall. I've left one very small comment.

For the hook, I would have gone with filtering the $can_manage_student value instead of filtering the user IDs to keep things simpler, but I'm OK either way. 🙂

[github-actions]

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