Fix identities management

[gaspergrom]

Changes proposed ✍️

What

🤖 Generated by Copilot at 852ca8a

This pull request improves the organization form page by fixing a bug with empty identity links and adding support for username and url fields for each identity. It also updates the frontend and backend data models to be consistent.
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🤖 Generated by Copilot at 852ca8a

The org form had a bug with the links
That showed up for some identities' blinks
So they added username and url
And refactored the data to unfurl
The backend API format for the syncs

Why

How

🤖 Generated by Copilot at 852ca8a

• Prevent empty links and enable identities only if they have a url in the organization form (link, link, link, link, link)
• Refactor the data structure of identities to match the backend model and simplify the input change handler (link)
• Add username and url properties to the identity objects passed to the OrganizationFormIdentities component in organization-form-page.vue (link)
• Map the identities array to the format expected by the backend API before saving or updating the organization in organization-form-page.vue (link)

Checklist ✅

• Label appropriately with Feature, Improvement, or Bug.
• Add screehshots to the PR description for relevant FE changes
• New backend functionality has been unit-tested.
• API documentation has been updated (if necessary) (see docs on API documentation).
• Quality standards are met.