Instead of relying on an intermediate `scep.Service` struct,
initialize the `scep.Authority` directly. This removes one redundant
layer of indirection.

When changing the SCEP configuration it is possible that one
or both of the decrypter configurations required are not available
or have been provided in a way that's not usable for actual SCEP
requests.

Instead of failing hard when provisioners are loaded,
which could result in the CA not starting properly, this type of
problematic configuration errors will now be handled at usage
time instead.

Instead of the old method that redacted sensitive information
by overriding the value of the property and changing it back
to the original, the API now uses a model specifically meant
for API responses. This prevents potential race conditions.

This may be iterated on a bit so that we don't need to rely
on the [provisioner.Interface] interface, which requires the
API model to implement unnecessary methods.

Add CSR to `SCEPCHALLENGE` webhook request body

…tep/certificates into herman/scep-provisioner-decrypter

Forgot to save the latest version...

…ifying-webhook

Add SCEP issuance notification webhook

…initialization

Change SCEP authority initialization

This commit uses the same types for the fields in the provisioner.SCEP
type and the "redacted" models.SCEP.

Fix redacted types in SCEP provisioner