The last of the four gaps ADR 0024 names. Everything the mesh handles
today it generated itself, sealed to both ends, and discarded. An API key
for a hosted service comes from a person, and carrying it needs a verb
the mesh did not have.
Accept seals it on the way in and keeps no plaintext — the same storage
and the same property as a generated one, only a different origin. That
is the whole difference from the arrangement being replaced, where an
operator-supplied key sits in a column the control plane can read, which
makes a copy of the database a copy of every account the mesh touches.
The consequence is deliberate: the mesh cannot show it back. Somebody who
loses the key gets a new one from wherever it came from. There is no
reveal and there cannot be one, because a mesh that can reveal a secret
is a mesh that holds it — asserted as a test, because it is a property
somebody will eventually ask to break.
An empty value is refused. A credential that exists, authenticates
nowhere and looks exactly like a working one is the failure this whole
mechanism is arranged to prevent.