Skia 6328b0c9e9 galaxy: use bulk_create whenever possible ...

This is a big performance gain, especially for the tests.

Examples:

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`./manage.py test galaxy.tests.GalaxyTest.test_full_galaxy_state`

Measurements averaged over 3 run on *my machine*™:
Before: 2min15s
After: 1m41s

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`./manage.py generate_galaxy_test_data --user-pack-count 1`

Before: 48s
After: 25s

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`./manage.py rule_galaxy` (for 600 citizen, corresponding to 1 user-pack)

Before: 14m4s
After: 12m34s

2023-05-10 12:15:19 +02:00

..

commands

galaxy: use bulk_create whenever possible

2023-05-10 12:15:19 +02:00