Found by raising a mesh end to end. The broker account a joining node
authenticates as is named after the node, and exists before that machine
has been told anything — so the node has to know its name before the mesh
can tell it. Without it, enrolment fails at the broker with an empty
username, which says nothing about why.
Not a secret, and the issuer already knows it. The wire-format test now
covers it, so a rename on either side fails in both repositories rather
than at enrolment on a real machine.
jschoubben
02d1020bce