Urls client cert auth (#18141)

* Build HTTPSClientAuthHandler more similarly to how HTTPSHandler works

* Add docs for new client cert authentication

* Support older versions of python

* Simplify logic

* Initial support for client certs in urls.py

* Add an extra test

* Add a get_url test for client cert auth

* Add additional test for client cert auth, with validation and ssl mismatch

* Skip assert when http tester not available

* Update version_added for new options

lib/ansible/modules/network/basics/get_url.py

@@ -156,6 +156,22 @@ options:
     required: false
     choices: [ "yes", "no" ]
     default: "no"
+  client_cert:
+    required: false
+    default: null
+    description:
+      - PEM formatted certificate chain file to be used for SSL client
+        authentication. This file can also include the key as well, and if
+        the key is included, I(client_key) is not required
+    version_added: 2.4
+  client_key:
+    required: false
+    default: null
+    description:
+      - PEM formatted file that contains your private key to be used for SSL
+        client authentication. If I(client_cert) contains both the certificate
+        and key, this option is not required.
+    version_added: 2.4
   others:
     description:
       - all arguments accepted by the M(file) module also work here