Serializer for creating a shareable SDK link.

This serializer validates the input data required to create a reusable shareable verification link. The link can be shared with multiple users, and each user who accesses the link will get their own unique verification session.

Required Fields: - widget_id: UUID of the widget configuration to use for verification

Optional Fields: - metadata: Custom JSON metadata to attach to the shareable link - sdk_base_url: Custom SDK base URL (defaults to production) - expires_at: Custom expiry timestamp (max 30 days, defaults to no expiry)

Note: first_name, last_name, email are not required for generating the shareable link. These will be auto-generated when users access the link.

Example Request Body: { "widget_id": "123e4567-e89b-12d3-a456-426614174000", "metadata": {"campaign": "onboarding_2024"}, "expires_at": "2024-12-31T23:59:59Z" }