Custom Units / Packs fixes

[awwaiid]

Fixes for #5096

• Allow a bank to have NO custom-units without breaking requests (with spec)
• Pluralize units on request confirmation
• Re-organize units display on the request detail page ("Adult Briefs (Medium/Large) - 33 snorves")
• Verify (maybe I fixed?) that Partner's Request History page shows units
• Capitalize units less
• Allow banks to create requests on-behalf-of partners (with units)

[cielf]

"First Thing" from the issue is still going BOOM!

[awwaiid]

@cielf I had previously fixed the wrong bug, sorry! Please try again :)

Now also:

• Removes forced-capitalization on units
• Fixes item_request.name_with_units for deleted items

[cielf]

Two more things....
1/ I just thought to test this -- you should not be able to enter unit as a custom unit, right? I don't know that it would break anything, but it's going to be confusing.
2/ Units is capitalized in the dropdown in request, and should not be.
Haven't tested the name with units issue live yet, but will.

[awwaiid]

• unit(s) is no longer allowed to be created as an organization unit (with spec)
• "Unit" is now "unit" for the default in the drop-down

[cielf]

This looks pretty good to me, functionally (Good enough for our beta tester). Over to @dorner for technical comments!

[dorner]

Non-blocking comment. This is good to merge!

[dorner]

@awwaiid can you look at the failing tests? I tried rerunning but they're still failing.

[cielf]

'Sall good. We'll need to add enable_packs to flipper for prod/staging, and turn it on for staging - but those staging changes can be a separate PR.