Refactor openssl_csr module, add openssl_csr_pipe module (#123)

* Extract doc fragment from openssl_csr.

* Refactor openssl_csr module into backend + module.

* Add openssl_csr_pipe module.

* Add seealso references.

* ...

* Use /dev/stdin instead of -, which seems to be only supported by newer openssl versions.

* Bump version.

* DRY: use select_message_digest.

* Fix deprecation version in docs.

* Docs improvements.

* Improve argument spec handling for module backends.

* Linting.

* Fix linting problems by using kwargs.

plugins/module_utils/crypto/module_backends/common.py

@@ -0,0 +1,30 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright: (c) 2020, Felix Fontein <felix@fontein.de>
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+from __future__ import absolute_import, division, print_function
+__metaclass__ = type
+
+
+from ansible.module_utils.basic import AnsibleModule
+
+
+class ArgumentSpec:
+    def __init__(self, argument_spec, mutually_exclusive=None, required_together=None, required_one_of=None, required_if=None, required_by=None):
+        self.argument_spec = argument_spec
+        self.mutually_exclusive = mutually_exclusive or []
+        self.required_together = required_together or []
+        self.required_one_of = required_one_of or []
+        self.required_if = required_if or []
+        self.required_by = required_by or {}
+
+    def create_ansible_module(self, **kwargs):
+        return AnsibleModule(
+            argument_spec=self.argument_spec,
+            mutually_exclusive=self.mutually_exclusive,
+            required_together=self.required_together,
+            required_one_of=self.required_one_of,
+            required_if=self.required_if,
+            required_by=self.required_by,
+            **kwargs)