Rewrite logic for AlekSIS/Django user/group sync to only save if necessary

This change refactors the code that ensures AlekSIS persons/groups are kept in sync with Django users/groups. Previously, the Django user object and all Djangogroup objects linked to a person were unconditionally saved on eache person save, which caused at least $number_of_groups+2 writes to the database (and as many haystack update tasks).

Now, we trace dirty fields (adding the django-dirtyfields library to ExensibleModel, so that we can rely on this feature in general) to decide whether to refresh the user object or not, and connect selectively to the m2m_changed signal on the members and owners relationships to decide which groups need refreshing.

Closes #350 (closed)

added part::backend workflow::discussing labels

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• b9a2f044 - Use django-dirtyfields to find out whether users and groups need to be saved

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• f426c334 - Remove stray import and fix syntax

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• 25099f94 - Get dirty fields at right point
• 34e2abd4 - Rewrite group syncing to Django as m2m signal

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• 5258031f - Move signal receiver out of class

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• 472add6d - Fix signal API for m2m_changed on Group membership

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• f1bef365 - De-bounce m2m_changed signal

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assigned to @hansegucker and unassigned @nik

requested review from @debdolph

marked this merge request as ready

changed the description

changed title from Resolve "[SQL] Frequent update of users in production, slow query" to Rewrite logic for AlekSIS/Django user/group sync to only save if necessary

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• 9756d708 - Update/add comments to new saving code

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added 3 commits

• ff39c78c - Use django-dirtyfields to find out whether users and groups need to be saved
• 2f370d42 - Rewrite group syncing to Django as m2m signal
• 63109344 - Update/add comments to new saving code

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This looks very fine.

approved this merge request

merged

mentioned in commit 624a2cdb

mentioned in issue #371 (closed)