feature: a VPN user has WireGuard peers, each a device with its public key and IPs, kept in the directory and written into wg0.conf by setup.

ADR.md

@@ -949,3 +949,23 @@ under the administrator's name. The directory becomes part of the system's name
 nslcd, and the system knows only the accounts with console login on. A user enrolled for TOTP types
 the code after the password at the SSH and sudo prompts. Homes are created at the first login and
 are not removed with the user. A password is changed through the directory, not with `passwd`.
+
+## ADR-35: WireGuard peers are the devices of the VPN users, kept in the directory
+
+Context: The WireGuard endpoint could be switched on from the Router Manager, but its peers were
+written by hand into `wg0.conf`, so nobody could connect without SSH. A peer is a P2S client like
+an OpenVPN or IKEv2 user, and one person may have several devices.
+
+Decision: A VPN user's entry holds the user's WireGuard peers in the multi-valued attribute
+`vpnRouterWireGuardPeer`, one value `<public key> <IP>[,<IP>...]` per device; the router never
+sees a private key. `PUT /users/<name>` replaces a user's peers after checking the keys, which
+are unique, and the IPs, which do not overlap another peer's or cover the router's address. Setup
+reads the peers of the users who are not disabled from the directory and writes them as a marked
+block of `[Peer]` sections into `wg0.conf`; sections outside the block, added by hand, stay. A
+change of the peers, and disabling, enabling or removing a user with peers, restart setup. The
+Router Manager adds and removes peers on the WireGuard tab of Remote access management, where the
+endpoint is, choosing the user for each.
+
+Consequences: Peers follow their users: disabling a user drops the user's devices, and the
+directory's backup holds them. A peer cannot exist without a VPN user. A change restarts
+`wg-quick@wg0` through setup, which briefly interrupts the other peers.