users: a user manages its own keys

Only a user who may manage users could change a user's keys: a user
couldn't add a new laptop's key, or remove a lost one.

A user now manages its own keys, whatever else it may do:

* GET /auth/keys: its keys, its entry, and the envelope holding it
  under a strict policy (`signed`), to sign against.
* PUT /auth/keys/{id} with an authorized_keys line, DELETE
  /auth/keys/{id}: one change, as the user. The rules take a write of
  _continuum/users/<name>/keys/… from the user it names.
* Under a strict policy, the user signs its entry with only its keys
  changed, with a key it holds already (envelope::check takes that from
  the user itself), PUT to its own entry even without write on the
  registry; continuum-signed key-add and key-remove do so.

0 files changed, 0 insertions, 0 deletions