Create a Certificate parameter

Up until now, Bytes parameter was used for certificate parameters
throughout the framework. However, the Bytes parameter does nothing
special for certificates, like validation, so this had to be done
for each of the parameters which were supposed to represent a
certificate.

This commit introduces a special Certificate parameter which takes
care of certificate validation so this does not have to be done
separately. It also makes sure that the certificates represented by
this parameter are always converted to DER format so that we can work
with them in a unified manner throughout the framework.

This commit also makes it possible to pass bytes directly during
instantiation of the Certificate parameter and they are still
represented correctly after their conversion in the _convert_scalar()
method.

https://pagure.io/freeipa/issue/4985

Reviewed-By: Fraser Tweedale <ftweedal@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>
Reviewed-By: Martin Basti <mbasti@redhat.com>

ipaserver/plugins/certmap.py

@@ -23,10 +23,9 @@ import dbus
 import six
 
 from ipalib import api, errors, x509
-from ipalib import Bytes
 from ipalib.crud import Search
 from ipalib.frontend import Object
-from ipalib.parameters import Bool, DNSNameParam, Flag, Int, Str
+from ipalib.parameters import Bool, DNSNameParam, Flag, Int, Str, Certificate
 from ipalib.plugable import Registry
 from .baseldap import (
     LDAPCreate,
@@ -39,7 +38,6 @@ from .baseldap import (
     pkey_to_value)
 from ipalib import _, ngettext
 from ipalib import output
-from ipaserver.plugins.service import validate_certificate
 
 
 if six.PY3:
@@ -521,8 +519,8 @@ class certmap_match(Search):
             if arg.name == 'criteria':
                 continue
             yield arg
-        yield Bytes(
-            'certificate', validate_certificate,
+        yield Certificate(
+            'certificate',
             cli_name='certificate',
             label=_('Certificate'),
             doc=_('Base-64 encoded user certificate'),