Integrate matrix-dynamic-dns with matrix-nginx-proxy without causing a dependency

We'd like the roles to be self-contained (as much as possible).

Thus, the `matrix-nginx-proxy` shouldn't reference any variables from
other roles. Instead, we rely on injection via
`group_vars/matrix_servers`.

Related to #681 (Github Pull Request)

group_vars/matrix_servers

@@ -851,6 +851,8 @@ matrix_ssl_architecture: "{{
 	}[matrix_architecture]
 }}"
 
+matrix_ssl_pre_obtaining_required_service_name: "{{ 'matrix-dynamic-dns' if matrix_dynamic_dns_enabled else '' }}
+
 ######################################################################
 #
 # /matrix-nginx-proxy

roles/matrix-nginx-proxy/defaults/main.yml

@@ -243,6 +243,10 @@ matrix_ssl_base_path: "{{ matrix_base_data_path }}/ssl"
 matrix_ssl_config_dir_path: "{{ matrix_ssl_base_path }}/config"
 matrix_ssl_log_dir_path: "{{ matrix_ssl_base_path }}/log"
 
+# If you'd like to start some service before a certificate is obtained, specify it here.
+# This could be something like `matrix-dynamic-dns`, etc.
+matrix_ssl_pre_obtaining_required_service_name: ~
+matrix_ssl_pre_obtaining_required_service_start_wait_time_seconds: 60
 
 # nginx status page configurations.
 matrix_nginx_proxy_proxy_matrix_nginx_status_enabled: false

roles/matrix-nginx-proxy/tasks/ssl/setup_ssl_lets_encrypt_obtain_for_domain.yml

@@ -12,17 +12,18 @@
 - set_fact:
     domain_name_needs_cert: "{{ not domain_name_certificate_path_stat.stat.exists }}"
 
-- name: Ensure dynamic dns has ran
+- block:
+  - name: Ensure required service for obtaining is started
     service:
-    name: "dynamic-dns"
+      name: "{{ matrix_ssl_pre_obtaining_required_service_name }}"
       state: started
-  register: dynamic_dns_service_update
-  when: "domain_name_needs_cert|bool and matrix_dynamic_dns_enabled|bool" 
+    register: matrix_ssl_pre_obtaining_required_service_start_result
 
-- name: Sleep for 60 seconds so that DNS records can be updated
+  - name: Wait some time, so that the required service for obtaining can start
     wait_for:
-    timeout: 60
-  when: dynamic_dns_service_update.changed
+      timeout: "{{ matrix_ssl_service_to_start_before_obtaining_start_wait_time_seconds }}"
+    when: "matrix_ssl_pre_obtaining_required_service_start_result.changed|bool"
+  when: "domain_name_needs_cert|bool and matrix_ssl_pre_obtaining_required_service_name != ''"
 
 # This will fail if there is something running on port 80 (like matrix-nginx-proxy).
 # We suppress the error, as we'll try another method below.