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

test/integration/targets/get_url/tasks/main.yml

@@ -211,3 +211,18 @@
   get_url: 
     url: https://{{ httpbin_host }}
     dest: "{{ output_dir }}"
+
+
+- name: Test client cert auth, with certs
+  get_url:
+    url: "https://ansible.http.tests/ssl_client_verify"
+    client_cert: "{{ output_dir }}/client.pem"
+    client_key: "{{ output_dir }}/client.key"
+    dest: "{{ output_dir }}/ssl_client_verify"
+  when: has_httptester
+
+- name: Assert that the ssl_client_verify file contains the correct content
+  assert:
+    that:
+      - 'lookup("file", "{{ output_dir }}/ssl_client_verify") == "ansible.http.tests:SUCCESS"'
+  when: has_httptester