Refactor time code, add tests, fix bug when parsing absolute timestamps that omit seconds (#745)

* Add time module utils.

* Add time helpers to ACME backend.

* Add changelog fragment.

* ACME timestamp parser: do not choke on nanoseconds.

plugins/module_utils/crypto/module_backends/certificate_selfsigned.py

@@ -14,7 +14,6 @@ import os
 from random import randrange
 
 from ansible_collections.community.crypto.plugins.module_utils.crypto.support import (
-    get_relative_time_option,
     select_message_digest,
 )
 
@@ -34,6 +33,10 @@ from ansible_collections.community.crypto.plugins.module_utils.crypto.module_bac
     CertificateProvider,
 )
 
+from ansible_collections.community.crypto.plugins.module_utils.time import (
+    get_relative_time_option,
+)
+
 try:
     import cryptography
     from cryptography import x509