We have a CSR authorizer plugin for calling to an IPC service.
In this commit we add test implementation of such a service.
We also remove the simple_csr_authorizer plugin and fold its
functionality into the new test_csr_authorizer functionality.
Add support for configuring the attributes of new principals created via
httpkadmind. This can be done via virtual host-based service
namespaces, which will provide default attributes even if disabled (but
the created principals will not be disabled, naturally), or via
krb5.conf.
Combined with the synthetic_clients feature, this will allow hosts that
have a PKINIT-worthy client certificate with a SAN with their host
principals to create their own principals and "extract" their host
keytabs. Together with some other PKIX credential bootstrapping
protocol, this can help hosts bootstrap Kerberos host credentials.
