docs(ocm): clarify contact removal semantics

IETF-OCM.md

@@ -1535,14 +1535,19 @@ such as HTTP 404.
 
 ## Recipient Removal
 
-A notification MAY be sent to inform a target OCM Server that a share
-recipient (e.g. a user or group) was removed from the list of trusted
-users, following a previous successful Invitation, or otherwise left
-the realm of the sending OCM Server.  That recipient may have been
-previously known to the target server because of existing shares whose
-shareType matched it.  The recipient of such notification SHOULD
-reciprocally remove that peer from the list of trusted users, along
-with any related shares.
+A notification MAY report a single contact removal, a user leaving
+the Sending Server's realm, or a group removal.
+
+For "CONTACT_REMOVED", the Receiving Server MAY reciprocally remove
+the contact between the two identified users. This notification alone
+MUST NOT withdraw or reject existing Shares in either direction, or
+affect other users' contacts. Each user MAY separately withdraw Shares
+they issued or decline Shares they received, using the corresponding
+per-share notifications.
+
+For "USER_REMOVED" and "GROUP_REMOVED", the Receiving Server SHOULD
+remove the departed recipient from its trusted users and related
+shares. A single contact removal MUST NOT be reported as user departure.
 
 For these cases, a notification payload is to be formed such that the
 `resourceType` MUST be omitted, the `shareType` is set to the affected
@@ -2101,6 +2106,7 @@ payload.
    | REQUEST_SHARE             | Resource  | This document |
    | USER_REMOVED              | Recipient | This document |
    | GROUP_REMOVED             | Recipient | This document |
+   | CONTACT_REMOVED           | Recipient | This document |
    +===========================+===========+===============+
 ~~~
 
@@ -2924,7 +2930,7 @@ The complete changelog is updated in the OCM-API GitHub repository.
 * Introduced an `apps` array in the `webapp` protocol payload, listing
   the available web applications each with the media types it can
   handle.  It replaces the `appName` and `mediaTypes` properties.
-* Introduced a CONTACT_REMOVAL notification.
+* Introduced a CONTACT_REMOVED notification.
 * Added reference to the OpenAPI protocol specification.
 
 ## Version 07