Administrators should be able to initiate account linking (attaching additional org identities to existing CO People). This requires at least two pieces:

(1) When no enrollment flows are defined, display a "+ Invite" or "+ Link" button for Org Identities on co_people/canvas, which allows the selection of an existing Org Identity (similar to basic enrollment).

(2) When enrollment flows are defined, need match type "select" (similar to relinking flows) to choose the CO Person to attach the new org identity to. Collect email address, require confirmation+authentication, then operate similar to self service. (Create an Enrollment Flow Template for this.)

Document both of these in the wiki.