Add self-check command

roles/matrix-server/tasks/self_check/self_check_client_api.yml

@@ -0,0 +1,20 @@
+---
+
+- set_fact:
+    matrix_client_api_url_endpoint_public: "https://{{ hostname_matrix }}/_matrix/client/versions"
+
+- name: Check Matrix Client API
+  uri:
+    url: "{{ matrix_client_api_url_endpoint_public }}"
+    follow_redirects: false
+  register: result_matrix_client_api
+  ignore_errors: true
+
+- name: Fail if Matrix Client API not working
+  fail:
+    msg: "Failed checking Matrix Client API is up at `{{ hostname_matrix }}` (checked endpoint: `{{ matrix_client_api_url_endpoint_public }}`). Is Synapse running? Is port 443 open in your firewall? Full error: {{ result_matrix_client_api }}"
+  when: "result_matrix_client_api.failed or 'json' not in result_matrix_client_api"
+
+- name: Report working Matrix Client API
+  debug:
+    msg: "The Matrix Client API at `{{ hostname_matrix }}` (checked endpoint: `{{ matrix_client_api_url_endpoint_public }}`) is working"