Prevent to delete a user if still has consumables associated to them

[inietov]

Description

If users have consumables assigned to them the system still let 'em to get deleted, which with other type of items is not permitted. This PR adds that functionality to the API and the 'normal' controller.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Test Configuration:

• PHP version: 8.1
• MySQL version: 8.0.23
• Webserver version: nginx/1.19.8
• OS version: Debian 10

Checklist:

• I have read the Contributing documentation available here: https://snipe-it.readme.io/docs/contributing-overview
• I have formatted this PR according to the project guidelines: https://snipe-it.readme.io/docs/contributing-overview#pull-request-guidelines
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[snipe]

Wait, since consumables can't be checked in ever, doesn't that mean that the user will never be able to be checked in?

[snipe]

(I may have to revert this change)

[snipe]

We could maybe add a setting where we determine what that behavior should be - delete consumables on user delete or put them back into stock. Seems like that behavior could vary a bit tho depending on the consumable. (I personally would think that if it's a consumable, you wouldn't put it back into stock when a user is deleted, since it will likely be at least partially used, and that gets us down a rabbit hole...)