Deleting one user flushes the whole entity cache for users

[indigoxela]

Description of the bug

Deleting a user should only affect the entity cache of that particular user, not flush everything as a whole.

This is a real pain point if your site has loads and loads of users and their profiles have lots of fields. Deleting one user makes the site (at least related pages) slow for a while.

Steps To Reproduce

1. Generate or create some users
2. Create a view of rendered users
3. Visit that views page - that's to trigger entity cache creation for all of them
4. Inspect Database table cache_entity_user - it should now be populated
5. Go to admin/people, pick one user
6. Cancel that single account - make sure you choose "Delete the account and its content"

Actual behavior

Inspect the database - the whole cache_entity_user table is empty.

Expected behavior

One row from the cache removed, the other ones untouched.

Additional information

• Backdrop CMS version: discovered in 1.29.2, but is reproducible in latest dev

[indigoxela]

It turned out, the solution's actually simple. Everything's in place in function user_delete_multiple(), only the parameter for the UIDs to delete was missing.

A PR is available for testing and review.