Multi-tenant plugin hides tenant selector when only one tenant exists, preventing users from choosing unassigned state

[DevAymen]

The multi-tenant plugin automatically hides the tenant dropdown selector when there's only one tenant available. This removes the user's ability to choose between assigning that tenant to a document or leaving the document unassigned to any tenant.

Current Behavior

• Multiple tenants: Tenant dropdown is visible, users can select a tenant or leave it unselected
• Single tenant: Tenant dropdown is completely hidden, the single tenant is automatically selected
• Zero choice: Users cannot create documents unassigned to any tenant when only one tenant exists

Expected Behavior
The tenant dropdown should always be visible regardless of tenant count, allowing users to:

1. Select the available tenant(s)
2. Choose to leave the document unassigned (null/empty state)
3. Maintain consistent UX whether they have 1 or multiple tenants

The issue stems from hardcoded conditions in plugin components:

// TenantSelectorClient component
if (options.length <= 1) {
    return null; // Hides the dropdown completely
}

// TenantField component  
if (options.length > 1) {
    return /* render field */;
}
return null; // No field rendered for single tenant