nginx/server: Extracted special pre directives into configurable vars

roles/nginx/server/defaults/main.yml

@@ -2,3 +2,14 @@
 
 # domain: example.com
 # directives: "server { … }"
+
+listen_directives: |
+  listen 443 ssl http2;
+  listen [::]:443 ssl http2;
+
+server_name_directives: |
+  server_name {{ domain }};
+
+certificates_directives: |
+  ssl_certificate {{ acme_certificate_location }};
+  ssl_certificate_key {{ acme_key_location }};

roles/nginx/server/templates/server.conf

@@ -1,10 +1,8 @@
 server {
-  listen 443 ssl http2;
-  listen [::]:443 ssl http2;
-  server_name {{ domain }};
+  {{ listen_directives | indent(width=2) }}
+  {{ server_name_directives | indent(width=2) }}
 
-  ssl_certificate {{ acme_certificate_location }};
-  ssl_certificate_key {{ acme_key_location }};
+  {{ certificates_directives | indent(width=2) }}
 
   include {{ nginx_snippets_directory }}/https;
   include {{ nginx_snippets_directory }}/global;