Delete a user attribute definition

Deletes a custom user attribute definition. Every value users hold for the attribute is removed with it. Any embed SSO login that still passes the attribute name then fails outright, locking out the organization's embed users until those URLs stop sending it; model SQL that references the attribute by name breaks; and a connection that selects an environment by that attribute name stops resolving one, so those users query the default connection instead. Requires the Manage User Attributes permission.