This change is to make easier the use of embedded authorities. It
can be difficult for third parties to know what fields are required.
The new init methods will define the minimum usable configuration.
When the CA is embedded in a third party product like Caddy, the
config needed to use placeholders to be valid. This change adds
a new method `NewEmbeddedAuthority` that allows to create an
authority with the given options, the minimum options are a root
and intermediate certificate, and the intermediate key.
Fixes#218
* authorize returns []interface{}
- operators in this list can conform to any interface the user decides
- our implementation has a combination of certificate claim validators
and certificate template modifiers.
* provisioners can set and enforce tls cert options
