Before this commit, EAB keys could be used CA-wide, meaning that
an EAB credential could be used at any ACME provisioner. This
commit changes that behavior, so that EAB credentials are now
intended to be used with a specific ACME provisioner. I think
that makes sense, because from the perspective of an ACME client
the provisioner is like a distinct CA.
Besides that this commit also includes the first tests for EAB.
The logic for creating the EAB JWS as a client has been taken
from github.com/mholt/acmez. This logic may be moved or otherwise
sourced (i.e. from a vendor) as soon as the step client also
(needs to) support(s) EAB with ACME.
- Each acme account has an index in this table. Before this change, the
index would grow unchecked as orders accumulate. This change removes
orders that have moved out of the 'PENDING' state.
