[login] Allow multiple projects on account requests

[Montekkundan]

Brief summary of changes

• Updates the Request Account form so users can select multiple projects.
• Saves every valid selected project to the requested account.
• Notifies relevant administrators for the selected projects at the chosen site.
• Preserves support for existing requests that submit a single project.
• Updates the Request Account test plan for multi-project registration.

Testing instructions

• Open http://localhost:8081/ and click Request Account.
• Confirm the Project field allows multiple selections and is required.
• Select two projects, complete the required fields, and submit the request.
• Confirm the success page appears.
• Confirm the requested account is associated with both selected projects in user_project_rel.
• Confirm relevant administrators for the selected projects and site receive only one notification.

Link(s) to related issue(s)

• Resolves [Login/Request_Account] Make Project multi-select #11138

[HachemJ]

Functionality wise, the PR looks good. I will approve it once the translation file cleanup is done.

The 'Project' label consistently appears in the singular form during my testing, despite the 'count: 2' parameter. This reminded me of a similar issue I encountered while working on the Biobank module, where Henri left the comment below #10801 (review). In that case, the fix was to revert to using the standalone 'Containers' key. We don’t currently have an equivalent standalone 'Projects' key here, so it may be worth looking into why the pluralization isn’t being applied correctly. This isn’t blocking the PR from my side, and I’ll approve it once the translation cleanup is done.

For future reference, I would also suggest adding a regression check to the testing instructions to confirm that the existing single project workflow still works when only one project is selected. I tested that case as well and it worked as expected, I tested that case as well and it worked as expected.

Thanks

[HachemJ]

LGTM!

[driusan]

@HachemJ dug into the problem a little more and the problem is that the English locale doesn't have a msgid_plural for "Projects" despite the loris.pot saying it should have a plural form.

I think the solution here is:

1. Go back to the "count: 99" to avoid needing to retranslate for every language
2. Add msgid_plural to locale/en/LC_MESSAGES/loris.po so that it correctly picks up the plural

[HachemJ]

@driusan thank you for the clarification. @Montekkundan can you please revert your last commit and fix the rest as instructed in the comment above? Thank you!

Note: Please assign this PR back to me so I can test it again when you are done.