feat(servers_config): add require statement to manage dependencies

Also, check config before applying

nginx/config.sls

     - context:
         config: {{ nginx.server.config|json(sort_keys=False) }}
 {% endif %}
-{% if nginx.check_config_before_apply %}
-    - check_cmd: /usr/sbin/nginx -t -c
-{% endif %}

nginx/servers_config.sls

       }}
     - makedirs: True
     - template: jinja
+      {%- if 'requires' in settings %}
+    - require:
+        {%- for k, v in settings.requires.items() %}
+      - {{ k }}: {{ v }}
+        {%- endfor %}
+      {%- endif %}
 {% if 'source_path' not in settings.config %}
     - context:
         config: {{ settings.config|json(sort_keys=False) }}

nginx/service.sls

       {% else %}
       - pkg: nginx_install
       {% endif %}
+{% if nginx.check_config_before_apply %}
+    - only_if: /usr/sbin/nginx -t
+{% endif %}

pillar.example

         # and None indicates no action
         enabled: true
 
+        # This let's you add dependencies on other resources being applied for a
+        # particular vhost
+        # A common case is when you use this formula together with letsencrypt's,
+        # validating through nginx: you need nginx running (to validate the vhost) but
+        # can't have the ssl vhost up until the certificate is created (because it
+        # won't exist and will make nginx fail to load the configuration)
+        #
+        # An example, when using LE to create the cert for 'some.host.domain':
+        # requires:
+        #   cmd: create-initial-cert-some.host.domain
+        requires: {}
+
         # Remove the site config file shipped by nginx
         # (i.e. '/etc/nginx/sites-available/default' by default)
         # It also remove the symlink (if it is exists).

test/salt/passenger/pillar/nginx.sls

       - location ^~ /.well-known/acme-challenge/:
           - proxy_pass: http://localhost:9999
   server:
-
     config:
       # This is required to get the passenger module loaded
       # In Debian it can be done with this
               - index: 'index.html index.htm'
               - location ~ .htm:
                   - try_files: '$uri $uri/ =404'
-              # - include: '/etc/nginx/snippets/letsencrypt.conf'
-              - include: 'snippets/letsencrypt.conf'
+              - include: '/etc/nginx/snippets/letsencrypt.conf'