openssh_keypair - Adding backend option and refactoring backend code (#236)

* Refactoring openssh_keypair for multiple backends

* Fixing cryptography backend validations

* Simplifying conditionals and excess variable assignments

* Fixing docs and adding cleanup for integration tests

* Fixing docs and public key validation bugs in crypto backend

* Enhancing cryptogagraphy utils to raise OpenSSHErrors when file not found

* Adding missed copyright and cleanup for idempotency test keys

* Fixing doc style

* Readding crypto/openssh for backwards compatibility

* Adding changelog fragment and final simplifications of conditional statements

* Applied initial review suggestions

tests/integration/targets/setup_bcrypt/meta/main.yml

@@ -0,0 +1,3 @@
+dependencies:
+  - setup_remote_constraints
+  - setup_pkg_mgr

tests/integration/targets/setup_bcrypt/tasks/main.yml

@@ -0,0 +1,24 @@
+---
+####################################################################
+# WARNING: These are designed specifically for Ansible tests       #
+# and should not be used as examples of how to write Ansible roles #
+####################################################################
+
+- name: Attempt to install dependencies for OpenSSH > 7.8
+  block:
+    - name: Ensure bcrypt 3.1.5 available
+      become: true
+      pip:
+        name: bcrypt==3.1.5
+        extra_args: "-c {{ remote_constraints }}"
+
+    - name: Register bcrypt version
+      command: "{{ ansible_python.executable }} -c 'import bcrypt; print(bcrypt.__version__)'"
+      register: bcrypt_version
+  ignore_errors: true
+
+- name: Ensure bcrypt_version is defined
+  set_fact:
+    bcrypt_version:
+      stdout: 0.0
+  when: bcrypt_version is not defined