Removes a user's direct group membership and their explicit website memberships for websites currently in the group. Both sets of rows are removed atomically. The request is idempotent: a retry, or a well-formed user ID with no matching membership rows, returns 200 with group_membership_removed: false and website_memberships_removed: 0.

Organization membership, membership in other groups, and website membership outside this group are preserved. If another group grants access to one of the same websites, that effective access remains through the other group even though the user's explicit website membership row is removed. Organization members return 409 because their organization-derived access would remain. Requires a global API key, and the API key's own user cannot be removed. The endpoint accepts no request body.

{
  "success": true,
  "group_membership_removed": true,
  "website_memberships_removed": 3
}