Switch to managing cronjobs with the Ansible cron module

As suggested in #65 (Github issue), this patch switches
cronjob management from using templates to using Ansible's `cron` module.

It also moves the management of the nginx-reload cronjob to `setup_ssl_lets_encrypt.yml`,
which is a more fitting place for it (given that this cronjob is only required when
Let's Encrypt is used).

Pros:
- using a module is more Ansible-ish than templating our own files in
special directories

- more reliable: will fail early (during playbook execution) if `/usr/bin/crontab`
is not available, which is more of a guarantee that cron is working fine
(idea: we should probably install some cron package using the playbook)

Cons:
- invocation schedule is no longer configurable, unless we define individual
variables for everything or do something smart (splitting on ' ', etc.).
Likely not necessary, however.

- requires us to deprecate and clean-up after the old way of managing cronjobs,
because it's not compatible (using the same file as before means appending
additional jobs to it)

roles/matrix-server/tasks/setup/ssl/setup_ssl_lets_encrypt.yml

@@ -1,5 +1,17 @@
 ---
 
+# This is a cleanup/migration task, because of to the new way we manage cronjobs (`cron` module) and the new script name.
+# This migration task can be removed some time in the future.
+- name: (Migration) Remove deprecated Let's Encrypt SSL certificate management files
+  file:
+    path: "{{ item }}"
+    state: absent
+  with_items:
+    - /usr/local/bin/matrix-ssl-certificates-renew
+    - /etc/cron.d/matrix-ssl-certificate-renewal
+    - /etc/cron.d/matrix-nginx-proxy-periodic-restarter
+
+
 #
 # Tasks related to setting up Let's Encrypt's management of certificates
 #
@@ -32,18 +44,44 @@
     loop_var: domain_name
   when: "matrix_ssl_retrieval_method == 'lets-encrypt'"
 
-- name: Ensure SSL renewal script installed
+- name: Ensure Let's Encrypt SSL renewal script installed
   template:
-    src: "{{ role_path }}/templates/usr-local-bin/matrix-ssl-certificates-renew.j2"
-    dest: "/usr/local/bin/matrix-ssl-certificates-renew"
+    src: "{{ role_path }}/templates/usr-local-bin/matrix-ssl-lets-encrypt-certificates-renew.j2"
+    dest: /usr/local/bin/matrix-ssl-lets-encrypt-certificates-renew
     mode: 0750
   when: "matrix_ssl_retrieval_method == 'lets-encrypt'"
 
-- name: Ensure periodic SSL renewal cronjob configured
-  template:
-    src: "{{ role_path }}/templates/cron.d/matrix-ssl-certificate-renewal.j2"
-    dest: "/etc/cron.d/matrix-ssl-certificate-renewal"
-    mode: 0600
+- block:
+  - name: Ensure periodic SSL renewal cronjob configured (MAILTO)
+    cron:
+      user: root
+      cron_file: matrix-ssl-lets-encrypt
+      env: yes
+      name: MAILTO
+      value: "{{ matrix_ssl_lets_encrypt_support_email }}"
+
+  - name: Ensure periodic SSL renewal cronjob configured (matrix-ssl-lets-encrypt-certificates-renew)
+    cron:
+      user: root
+      cron_file: matrix-ssl-lets-encrypt
+      name: matrix-ssl-lets-encrypt-certificates-renew
+      state: present
+      hour: 4
+      minute: 15
+      day: "*/5"
+      job: /usr/local/bin/matrix-ssl-lets-encrypt-certificates-renew
+
+  - name: Ensure periodic reloading of matrix-nginx-proxy is configured for SSL renewal (matrix-nginx-proxy-reload)
+    cron:
+      user: root
+      cron_file: matrix-ssl-lets-encrypt
+      name: matrix-nginx-proxy-reload
+      state: present
+      hour: 4
+      minute: 20
+      day: "*/5"
+      job: /usr/bin/systemctl reload matrix-nginx-proxy.service
+    when: matrix_nginx_proxy_enabled
   when: "matrix_ssl_retrieval_method == 'lets-encrypt'"
 
 
@@ -51,11 +89,26 @@
 # Tasks related to getting rid of Let's Encrypt's management of certificates
 #
 
-- name: Ensure Let's Encrypt SSL certificate management files removed
-  file:
-    path: "{{ item }}"
+# When nginx-proxy is disabled, make sure its reloading cronjob is gone.
+# Other cronjobs can potentially remain there (see below).
+- name: Ensure matrix-nginx-proxy-reload cronjob removed
+  cron:
+    user: root
+    cron_file: matrix-ssl-lets-encrypt
+    name: matrix-nginx-proxy-reload
+    state: absent
+  when: "not matrix_nginx_proxy_enabled"
+
+# When Let's Encrypt is not used at all, remove all cronjobs in that cron file.
+- name: Ensure matrix-ssl-lets-encrypt-renew cronjob removed
+  cron:
+    user: root
+    cron_file: matrix-ssl-lets-encrypt
     state: absent
-  with_items:
-    - /usr/local/bin/matrix-ssl-certificates-renew
-    - /etc/cron.d/matrix-ssl-certificate-renewal
   when: "matrix_ssl_retrieval_method != 'lets-encrypt'"
+
+- name: Ensure Let's Encrypt SSL renewal script removed
+  file:
+    path: /usr/local/bin/matrix-ssl-lets-encrypt-certificates-renew
+    state: absent
+  when: "matrix_ssl_retrieval_method != 'lets-encrypt'"