Resolve "Django 3.2 database improvements"

Closes #125 (closed)

added part::backend label

added 4 commits

• 59886687 - Update poetry.lock
• af46a31c - Limit selected fields in build_timetable
• 7206d283 - Prefer alias instead of annotate and remove superfluous annotations
• 05b034dd - Add some (convering) indexes to speed up database queries

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Functional index on ExtraLesson: TO_DATE(CONCAT("chronos_extralesson"."year", "chronos_extralesson"."week"), 'IYYYIW'), including week, year, period_id, subject_id, room_id, comment

added 30 commits

• 05b034dd...577c6da3 - 29 commits from branch master
• 6a92a2ee - Merge branch 'master' into 125-django-3-2-database-improvements

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added 4 commits

• 6a92a2ee...62262dff - 2 commits from branch master
• d4eeb1ef - Fix lint
• 39235e09 - Merge branch 'master' into 125-django-3-2-database-improvements

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marked this merge request as ready

mentioned in commit edd54e90

merged