feat: Platform API improvements (#2900)

- Platform APIs to add and update custom attributes to users
- Platform APIs to delete accounts
- Platform APIs to delete users

app/views/api/v1/models/_agent.json.jbuilder

@@ -4,6 +4,7 @@ json.confirmed resource.confirmed?
 json.email resource.email
 json.available_name resource.available_name
 json.id resource.id
+json.custom_attributes resource.custom_attributes if resource.custom_attributes.present?
 json.name resource.name
 json.role resource.role
 json.thumbnail resource.avatar_url