users: a user can't remove its own last key

A user managing its own keys (1168) could remove the last, and then
neither sign nor log in by key. It can't now: DELETE /auth/keys/{id}
of the last answers 409, the rules take a user's change of its own keys
only with one left after it, and under a strict policy its own entry
signed only with one key at least. One who may manage users still may.

1 files changed, 2 insertions, 1 deletions

diff --git a/docs/access.md b/docs/access.md
index a8dfed4..5941bdb 100644
--- a/docs/access.md
+++ b/docs/access.md
@@ -36,7 +36,8 @@ password hashes: every member reads the document).
   with the line, `DELETE /auth/keys/<name>`; under a strict policy, by signing its
   entry with only its keys changed (`continuum-signed key-add laptop
   ~/.ssh/id_ed25519.pub`, `key-remove laptop`), with a key it holds already. Every
-  node takes that from the user itself, as from one who may manage users.
+  node takes that from the user itself, as from one who may manage users, but never
+  its last key removed (`409`): one who may manage users may.
 
 ## A new swarm