staging hotfix: [UIE-9137] - AssignSelectedRolesDrawer user selection state issue

[abailly-akamai]

Description 📝

This PR fixes a couple issues with the behavior of the AssignSelectedRolesDrawer component - specifically the user selection.

Prior to this fix we would encounter two issues:

• After an initial user selection from the drop down, pressing the "Assign" CTA would result in a validation error that would require a subsequent selection to allow the form to submit
• The form would over-fetch: when selecting a user from the dropdown, we could see another unnecessary fetch to the account/users endpoint due to the filter changing based on the value.

While a dedicated state input state was the right model, there was no need for detaching the actual username from the form state

Changes 🔄

• Clean up AssignSelectedRolesDrawer state 👉 rely on form state for actual username
• Comment behavior

Scope 🚢

Upon production release, changes in this PR will be visible to:

• All customers
• Some customers (e.g. in Beta or Limited Availability)
• No customers / Not applicable

Target release date 🗓️ 8/26/2025

Preview 📷

How to test 🧪

Prerequisites

IAM account with permission to assign roles to another user

Reproduction steps

• Go to /iam/roles
• Click Assign Role button next to any role
• Select any username in the user selector
  • ⛔ Notice account/users is being refetched
• Click the Assign button
  • ⛔ Notice inline validation error

Verification steps

• Go to /iam/roles
• Click Assign Role button next to any role
• Select any username in the user selector
  • ✅ Notice account/users is NOT being refetched
• Click the Assign button
  • ✅ Notice NO inline validation error and form submits

Also confirm fetching by any username still works ✅

Author Checklists

As an Author, to speed up the review process, I considered 🤔

👀 Doing a self review
❔ Our contribution guidelines
🤏 Splitting feature into small PRs
➕ Adding a changeset
🧪 Providing/improving test coverage
🔐 Removing all sensitive information from the code and PR description
🚩 Using a feature flag to protect the release
👣 Providing comprehensive reproduction steps
📑 Providing or updating our documentation
🕛 Scheduling a pair reviewing session
📱 Providing mobile support
♿ Providing accessibility support

• I have read and considered all applicable items listed above.

As an Author, before moving this PR from Draft to Open, I confirmed ✅

• All tests and CI checks are passing
• TypeScript compilation succeeded without errors
• Code passes all linting rules

[aaleksee-akamai]

looks good, the issue has beed resolved, thanks @abailly-akamai

[kwojtowiakamai]

Looks good. Thanks for fixing it so quickly! @abailly-akamai

[linode-gh-bot]

Cloud Manager UI test results

🎉 735 passing tests on test run #2 ↗︎

❌ Failing	✅ Passing	↪️ Skipped	🕐 Duration
0 Failing	735 Passing	4 Skipped	124m 51s

[coliu-akamai]

✅ confirmed no more refetching
✅ confirmed fix

thanks @abailly-akamai!